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| United States Patent |
5,709,958
|
|
Toyoda
, et al.
|
January 20, 1998
|
Electronic parts
Abstract
An electronic part comprising an amorphous thin film formed on a substrate;
and a metal wiring formed on the surface of the amorphous thin film;
wherein an interatomic distance corresponding to a peak of halo pattern
appearing in diffraction measurement of the amorphous thin film
approximately matches with a spacing of a particular crystal plane defined
with the first nearest interatomic distance of the metal wiring. An
electronic part provided with a metal wiring formed of highly orientated
crystal wherein half or more of all grain boundaries are small angle grain
boundaries defined by one of grain boundaries with a relative
misorientation of 10.degree. or less in tilt, rotation and combination
thereof around orientation axes of neighboring crystal grains; coincidence
boundaries where a .SIGMA. value is 10 or less; and grain boundaries with
a relative misorientation of 3.degree. or less from the coincidence
boundary. A method for manufacturing an electronic part, comprising the
step of depositing a conductor layer which is mainly formed of one
selected from Al and Cu on a substrate via an insulative layer, a barrier
layer, a contact layer or an amorphous thin film layer wherein one element
selected from Ga, In, Cd, Bi, Pb, Sn and Tl is supplied before or during
the deposition of the conductor layer.
| Inventors:
|
Toyoda; Hiroshi (Kokohama, JP);
Kaneko; Hisashi (Fujisawa, JP);
Hasunuma; Masahiko (Yokohama, JP);
Kawanoue; Takashi (Yokohama, JP);
Tomita; Hiroshi (Hadano, JP);
Kajita; Akihiro (Yokohama, JP);
Miyauchi; Masami (Yokohama, JP);
Kawakubo; Takashi (Yokohama, JP);
Ito; Sachiyo (Yokohama, JP)
|
| Assignee:
|
Kabushiki Kaisha Toshiba (Kanagawa-ken, JP)
|
| Appl. No.:
|
451528 |
| Filed:
|
May 26, 1995 |
Foreign Application Priority Data
| Aug 27, 1992[JP] | 4-228264 |
| Apr 15, 1993[JP] | 5-0800108 |
| Current U.S. Class: |
428/620; 257/E23.16; 428/641; 428/642 |
| Intern'l Class: |
H01L 029/43 |
| Field of Search: |
428/620,601,641,642,650,672,630,686,426,427,428,433,434,210
|
References Cited
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| 4352239 | Oct., 1982 | Pierce | 29/590.
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| 4742014 | May., 1988 | Hooper et al. | 437/192.
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| 4942451 | Jul., 1990 | Tamaki et al. | 357/67.
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| 4965656 | Oct., 1990 | Koubuchi et al. | 357/71.
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| 4970574 | Nov., 1990 | Tsunenari | 357/71.
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| 5011732 | Apr., 1991 | Takeuchi et al. | 428/209.
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| 5051812 | Sep., 1991 | Onuki et al. | 357/71.
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| 5110637 | May., 1992 | Ando et al. | 428/34.
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| 5187561 | Feb., 1993 | Hasunuma et al. | 257/771.
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| 5233217 | Aug., 1993 | Dixit et al. | 257/530.
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| 5296297 | Mar., 1994 | Servais et al. | 428/426.
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| 5339435 | Aug., 1994 | Ando et al. | 428/428.
|
| 5409862 | Apr., 1995 | Wada et al. | 437/197.
|
| 5498909 | Mar., 1996 | Hasunuma et al. | 257/754.
|
| Foreign Patent Documents |
| 0 326 018 A3 | Aug., 1989 | EP.
| |
| 0 465 264 A3 | Jan., 1992 | EP.
| |
| 0 510 969 A3 | Oct., 1992 | EP.
| |
| 5524754 A3 | Jan., 1993 | EP.
| |
| 64-37051 | Jul., 1987 | JP.
| |
| WO A 81 01629 | Jun., 1981 | WO.
| |
Other References
"Microstructure and Magnetic Properties of CoCr Thin Films Formed on Ge
Layer", Futamoto et al., IEEE Transactions on Magnetics, vol. MAG-21, No.
5, pp. 1426-1428, Sep. 1985.
"Electromigration Characteristics of Vias in Ti:W/ALcu (2st%) Multilayered
Metallization", J. May, IEEE Reliability Physics 1991 No Month, Cat No.
91CH2974-4.
"A Quarter-Micron Interconnection Technology Using Al-Si-Cu/TiN Alternated
Layers", T. Kikkawa, et al., IEEE Int'l Electron Devices Meeting (1991) No
Month.
Tungsten/Titanium Nitride Low-Resistance Interconnections Durable for High
Temperature Processing, Nakasaki et al., Journal of Applied Physics (1988)
No Month.
Electromigration Phenomena in Al-Si and Al-V-Si Thin Alloy Films, P. Van
Engelen et al., Thin Solid Films, pp. 999-1007 (1990) No Month.
Studies of the Interaction Between Aluminum and Nickel, Chromium Andrnated
Nichrome Alloy Films, A Gershiniski, Thin Solid Films, pp. 171-181 (1988)
No Month.
A Candidate for Interconnection Material, Al-Y Alloy Thin Films, Y. Ki Lee,
et al., Materials Letters, vol. 10, No. 7,8, pp. 344-347 (1991) No Month.
Hideaki Shimamura et al., "Microstructure of Sputter-Deposited Al-Cu-Si
Films"; May, 1991; Journal of Vacuum Science Technology: Part A; vol. 9,
No. 3, Part 1, pp. 595-599.
H. Shibata et al., "Influence of Under-Metal Planes on Al(111) Crystal
Orientation in Layerd A1 Conductors"; May 28,1991; Proceedings of the
Symposium on VLSI Technology; OISO; No. Symp. 11; Institute of Electrical
and Electrtonics Engineers; pp. 33-34.
|
Primary Examiner: Zimmerman; John J.
Attorney, Agent or Firm: Finnegan, Henderson, Farabow, Garrett & Dunner, L.L.P.
Parent Case Text
This is a divisional application of Ser. No. 08/314,493 filed Sep. 28, 1994
pending, which is a continuation-in-part of application of Ser. No.
08/112,210 filed Aug. 26, 1993, now abandoned, the disclosures of which
are incorporated by reference.
Claims
What is claimed is:
1. An electronic part comprising:
a substrate; and
a metal wiring formed on the substrate;
wherein the metal wiring is formed of highly oriented crystals in which at
least half of all grain boundaries are small angle grain boundaries, said
small angle grain boundaries defined as one of: grain boundaries with a
relative misorientation of 10.degree. or less in tilt, rotation, or a
combination thereof around orientation axes of neighboring crystal grains;
coincidence boundaries having a .SIGMA. value of 10 or less; and grain
boundaries with a relative misorientation of 3.degree. or less from the
coincidence boundaries.
2. The electronic part of claim 1, wherein the metal wiring is mainly
formed of one metal selected from the group consisting of Al, Cu, Au, Ag,
and W.
3. The electronic part of claim 1, wherein the metal wiring comprises an
alloy selected from the group consisting of an Al--Cu alloy, an Al--Ti
alloy, an Al--Cr alloy, an Al--Ta alloy, an Al--Mg alloy, an Al--In alloy,
an Al--Li alloy, a Cu--Be alloy, a Cu--Ag alloy, an Au--Pt alloy, an
Au--Ag alloy, an Au--Pd alloy, and an Au--Cu alloy.
4. The electronic part of claim 3, wherein the alloy further comprises Si
in an amount of 1 wt % or less.
5. The electronic part of claim 1, wherein the grain boundaries contain an
element selected from the group consisting of Ga, In, Cd, Bi, Pb, Sn, and
Tl.
6. The electronic part of claim 1, wherein the metal wiring is formed on
the surface of an amorphous thin film of metal, and wherein an interatomic
distance of the amorphous thin film in an ordered structure in a short
range, which is determined from a peak of a halo pattern appearing in a
diffraction measurement, approximately matches a spacing of a particular
crystal plane including atoms with the first nearest interatomic distances
of the metal wiring.
7. An electronic part comprising:
a substrate;
a metal wiring formed on the substrate; and
a pad part formed on the substrate, connected to the metal wiring, and
comprised of an aggregation of fine lines which are successively branched
from the metal wiring,
wherein the metal wiring and the pad part are formed of crystals selected
from the group consisting of single crystals and highly oriented crystals
in which at least half of all grain boundaries are small angle grain
boundaries having a low grain boundary energy, said small angle grain
boundaries defined as one of: grain boundaries with a relative
misorientation of 10.degree. or less in tilt, rotation, or a combination
thereof around orientation axes of neighboring crystal grains; coincidence
boundaries having a .SIGMA. value of 10 or less; and grain boundaries with
a relative misorientation of 3.degree. or less from the coincidence
boundaries.
8. The electronic part of claim 7, wherein the metal wiring and the pad
part are formed on the surface of an amorphous thin film of metal, and
wherein an interatomic distance of the amorphous thin film in an ordered
structure in a short range, which is determined from a peak of a halo
pattern appearing in a diffraction measurement, approximately matches a
spacing of a particular crystal plane including atoms with the first
nearest interatomic distances of the metal wiring.
9. The electronic part of claim 7, wherein a width of each of the fine
lines is wider than that of the metal wiring.
10. The electronic part of claim 7, wherein the branched fine lines are
connected with a connecting fine line running perpendicular to the
branched fine lines.
11. The electronic part of claim 7, wherein a current density of the pad
part is one tenth or more of a current density of the metal wiring.
12. The electronic part of claim 7, wherein the crystals orient in such a
manner than an angle formed between the normal line direction of the
close-packed plane of each crystal grain and the normal line direction of
the bottom surface of the metal wiring is 80.degree. or less.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to electronic parts such as integrated
circuit (IC) devices, and particularly to electronic parts with metal
wiring having higher reliability e.g., the improved electromigration
endurance, and manufacturing method thereof.
2. Description of the Related Art
Recently integration in memory IC devices represented by D-RAMs has been
increasing. With the increase, wiring electrically connecting between
elements becomes finer. This fineness requires wiring for a higher current
density and operating temperature. At the same time, wiring is required
for the further improved electromigration endurance, thereby attaining
high reliability. However, the electromigration endurance is inversely
proportional to a current density and operating temperature. At present, a
thin film made of metal such as Al or Al alloys is frequently used for
wiring. The electromigration endurance of such metal wiring has been
improved by addition of a transition metal such as Cu or Ti in a trace
quantity or the bamboo sheath-like grain structure (bamboo structure)
which is caused by crystal grain growth. However, it is difficult to
attain the reliability of wiring on the order of 0.1 micron only by this
improvement in electromigration endurance. Recent investigations revealed
that the electromigration endurance and stress-migration endurance due to
tensile stress introduced in wiring were remarkably increased by a
single-crystal wiring. As a means for attaining high reliability, it is
considered that the crystalline properties of a metal thin film are as
near to those of single crystal as possible.
At present, in electronic parts such as memory IC devices, metal wiring is
formed on the surface of an amorphous thin film generally represented by a
SiO.sub.2 interlayer insulative film with or without a barrier layer. Thus
a metal thin film with the high crystalline properties cannot be formed by
a so-called epitaxial crystal growth method where a single-crystal thin
film can be grown by continuing the crystalline arrangement of an
underlayer. As a result, metal wiring with the excellent electromigration
endurance and high reliability is hardly obtained.
As described above, there is a problem that conventional electronic parts
hardly have metal wiring with the high reliability.
SUMMARY OF THE INVENTION
An object of the invention is to provide electronic parts allowing finer
elements, higher integration, higher current density, and higher
temperature of operation conditions.
Another object of the invention is to provide electronic parts with highly
reliable metal wiring obtained by the formation of a metal thin film with
the high crystalline properties.
A further object of the invention is to provide electronic parts with
highly reliable metal wiring obtained by an underlying layer of which
electrical resistance in a contact part is satisfactorily low and which
can be easily processed, and a metal thin film with the high crystalline
properties formed on the underlying layer.
A still further object of the invention is to provide electronic parts with
highly reliable metal wiring simultaneously preventing wiring failures and
shortcircuit.
A still further object of the invention is to provide electronic parts with
metal wiring with the improved electromigration and stress-migration
endurance.
A big problem for obtaining a metal thin film with the high crystalline
properties is that many crystal nucleuses, from which growth of thin films
will start, are simultaneously formed on an underlying layer to be
deposited thereon at an initial stage of the deposition. At a film-growing
stage, crystal growth of these crystal nucleuses is advanced by absorbing
deposited particles or uniting with other nucleuses. However, the size of
the crystal nucleuses growing by this mechanism is limited. A finally
obtained thin film is of polycrystalline where individual crystal grains
have different orientation arrangements. Accordingly, in order to form a
thin film with the high crystalline properties in a large region, it is
important to suppress occurrence of nucleuses as low as possible.
Here, the occurrence of nucleuses is considered based on classic argument.
In the case where the surface/interfacial energy relationship between a
deposited material and underlying material as shown in the equation (1) is
satisfied (a wetting angle is zero), so-called layer growth can be
attained and the density of nucleuses occurrence becomes zero.
.gamma.f.ltoreq..gamma.s-.gamma.i (1)
.gamma.f: the surface energy of a deposited material
.gamma.s: the surface energy of an underlying material
.gamma.i: the interfacial energy
Here, it is said that the interfacial energy .gamma.i depends on 1) lattice
matching of a deposited material and underlying material, and 2)
interatomic bonding energy between a deposited material and underlying
material, in crystal-crystal interface. However, in the case where an
amorphous material is used as an underlying material like at the time of
forming metal wiring in semiconductor devices, it has not been found on
what the surface energy of underlying material and interfacial energy
depends.
The inventors have eagerly investigated and examined relationships of
atomic arrangement at an interface in detail. As a result, it was found
that atomic or molecular arrangement at an interface significantly
effected crystal arrangement of a deposited material in the case where an
amorphous material is used as an underlying layer as well. Namely,
diffraction by X-ray, electron beam and the like revealed that even in an
amorphous material, the structure thereof is not completely disordered and
there exists regular structure in a short range. As described above, the
magnitude of interfacial energy, which determines atomic arrangement at an
interface, is determined by the degree of lattice matching of 2 to 3
periods. This short range order is substantially the same as an
interatomic distance corresponding to a peak of halo pattern which appears
in diffraction measurement of an amorphous material. Thus, in this
invention, it was found that this interatomic distance was matched with
the spacing of atoms or molecules of a deposited material so that
interface energy could be reduced, resulting in the formation of a thin
film with the very high crystalline properties.
An electronic part of the present invention comprises an amorphous thin
film formed on a substrate, and a metal wiring formed directly on the
amorphous thin film, wherein an interatomic distance of the amorphous thin
film in an ordered structure in a short range, which is determined from a
peak of halo pattern appearing in a diffraction measurement, approximately
matches with a spacing of a particular crystal plane including atoms with
the first-nearest interatomic distance of the metal wiring. The particular
crystal plane including atoms with the first-nearest interatomic distance
defined in the above comprises, (111), (200) or (220) in face-centered
cubic lattice (fcc), (110) in body-centered cubic lattice (bcc), and (002)
or (110) in hexagonal close-packed lattice (hcp). The first nearest
interatomic distance of these particular planes is illustrated in FIG. 36.
At this time, it is most preferable that the interatomic distance ds of
the amorphous thin film matches with the spacing df of the metal wiring.
However, a slight dismatch is allowed and the following equation is
preferably satisfied;
.vertline.df-ds.vertline./ds.ltoreq.0.25
The particular crystal plane is not limited to an orientated plane.
Composition of the amorphous thin film varies the degree of match. If the
amorphous thin film contains an element mainly constituting the metal
wiring, a better matching can be obtained.
Another factor controlling interfacial energy is bonding energy as well as
a crystal-crystal system. In other words, increase in bonding energy can
reduce interfacial energy. Thus, the amorphous thin film preferably
contains an element M of which the menal wiring is mainly made. Otherwise,
the amorphous thin film preferably contains an element A forming an
intermetallic compound with the element M, or an element B capable of
continuous series of solid solution with the element M or having the range
allowing a complete solid solution. Here, Al, Cu, Au, Ag, or W can be
generally used as an element M.
As surface energy .gamma.s of an underlying material increases, a deposited
material is more easily layer-like grown. However, since the surface
energy is measured around the melting point of a material, it is
substantially impossible to measure the surface energy of an amorphous
material, because a crystallization temperature is lower than a melting
point. It was examined what influences the surface energy of an amorphous
material. As a result, it was found that it related with the surface
energy thereof in a crystal state. That is, in order to increase the
surface energy .gamma.s of an underlying material, the surface energy of a
material in a crystal state constituting the amorphous thin film is
preferably larger than the surface energy of a material constituting metal
wiring (deposited material). Thus, the melting point, roughly proportional
to the surface energy, of a material in a crystal state constituting the
amorphous thin film is desirably high. Here, the surface energy of an
amorphous material formed of a plurality of elements is defined as the sum
of the fractional surface energies of individual elements.
Substrates of the invention are not particularly limited. Conventional
semiconductor substrates such as a Si substrate and GaAs substrate, and
glass substrates with and without ITO may be used. The shape thereof may
be flat or have grooves.
For example, simple metals, alloys or conductive compounds capable of being
amorphous are used for an amorphous thin film formed on a substrate.
Further, they preferably have composition containing at least one of the
above-mentioned elements M, A, and B. Considering the ability of forming
amorphous, transition metals, metalloids, semiconductor alloys, and
semiconductor compounds are preferable.
Concretely there are compositions containing two or more materials selected
from a metal element M, III B group elements (Sc, Y, Lanthanide), IV B
group elements (Ti, Zr, Hf), V B group elements (V, Nb, Ta), VI B group
elements (Cr, Mo, W), VIII group elements (Fe, Ru, Os, Co, Rh, Ir, Ni, Pd,
Pt), B, C, N, O, P, Si, and Ge. Compounds with perovskite type oxide
compositions can be used as an amorphous thin film.
Amorphous thin films used in this invention are an amorphous thin film
where a broad diffraction intensity, namely halo peak, can be measured in
diffraction measurements represented by electron diffraction such as RHEED
and X-ray diffraction. Diffraction lines from fine crystals such as
intermetallic compounds due to incomplete amorphous state are allowed for
amorphous thin films used in this invention. Further amorphous thin films
used in this invention are not required to be entirely amorphous.
Crystalline thin films of which only the surface is amorphous may be used.
The thickness thereof is preferably thin, more preferably 10 to 1000 .ANG..
However, even if thickness of 1000 .ANG. or more, the crystalline
properties of metal thin film formed thereon can be improved.
As shown in FIG. 2, this amorphous thin film 3 can be used not only as an
underlying layer for a single-layer wiring but also as an underlying layer
for each metal wiring 2 constituting multi-layer wirings. In addition, the
film 3 can be used as an under-layer for a conductive connecting part in
the longitudinal direction such as a via 4 or through hole. Further, the
film 3 may be formed directly on the substrate 1; or on an interposed
layer, for example, an insulative layer 5 such as a SiO.sub.2 thermal
oxide film, a barrier layer 6 of Ti, TiN or the like, a contact layer or
another wiring above the substrate 1. Here, the interposed layer may be
flat or have grooves. In this drawing, reference numeral 5 indicates an
insulative film such as SiO.sub.2 destined for an element isolation area,
and reference numeral 7 indicates a doped layer.
Further, according to the present invention, the formation of an amorphous
thin film as an underlying layer for metal wiring can considerably reduce
the number of hillocks caused by thermal treatment or electromigration.
It is generally thought that hillocks normally take place due to
compressive stress introduced in a thin film or metal wiring. Excess
volume generating compressive stress is released as hillocks. A point
where a hillock takes place is a point where stress is concentrated.
Endurance against deformation of a thin film at this stress-concentrated
point determines whether a hillock takes place or not. Since the
conventional W or TiN thin film is of a polycrystal, crystal grain
boundaries act as stress concentration parts, and cause cracks, and at
these parts hillocks take place.
The inventors found that amorphous state could overcome the above inherent
drawback of polycrystal. In other words, the use of amorphous thin film
can increase deformation endurance in a stress concentrated part where a
hillock may take place, thereby remarkably suppressing of hillocks can be
attained. In the case where an amorphous thin film contains the previously
mentioned element M, A or B, this effect is particularly remarkable. In
this case, the reasons therefor are thought that since the bonding energy
between a main element forming metal wiring and element in an amorphous
thin film increases, concentrated compressive stress generated in the
metal wiring can be uniformly distributed in the amorphous thin film,
resulting in considerable decrease in frequency of hillock occurrence.
In the above-mentioned view of preventing occurrence of hillocks, an
amorphous thin film is not required to be formed as an underlying layer
for metal wiring, but may coat a part of metal wiring. For example, as
shown in FIGS. 3(a), (b), (c), and (d), an amorphous thin film 101 may be
formed in the upper part or periphery of metal wiring 100. In the case
where an amorphous thin film is formed in the upper part of a metal film,
since the effect of preventing hillocks depends on an interatomic bonding
energy between the amorphous thin film and metal wiring, this effect
necessarily depends on the surface state of the metal wiring prior to the
formation of the amorphous thin film. For example, in the case of metal
wiring mainly formed of Al, the surface is generally coated with an Al
oxide. This can be confirmed by reflection high-energy electron
diffraction (RHEED). Namely, RHEED observation on the surface of an Al
wiring which have been exposed to the air indicates the following facts;
Since an amorphous oxide film is formed on the Al wiring surface, only a
halo pattern peculiar to be amorphous is obtained. However, if the surface
layer is removed by Ar sputtering, a ring or orientated diffraction
pattern of an Al thin film can be obtained. If an amorphous thin film is
formed after such process of the Al metal surface, the hillock suppressing
ability is further enhanced.
In the case where Cu is used for metal wiring as a low resistance wiring
material, there is a problem of oxidation endurance against O.sub.2 asher
in a resist removal step. At this time, particular amorphous thin films
containing Ti, Zr, Hf, V, Ta or Nb suppress distribution of oxygen into
the film through grain boundaries, and improves the oxidation endurance of
Cu.
According to the invention, the formation of an amorphous thin film between
a substrate and metal wiring can suppress reactions caused by grain
boundary diffusion in conventional technique. Among others, an Al
amorphous alloy as an amorphous thin film does not form a high resistance
reactive layer with metal wiring mainly formed of Al, resulting in a high
reliable contact part. Further, if an alloy containing one of Ta, Nb, V,
Mo and W is used as an Al amorphous alloy, a simultaneous fine wiring
process for metal mainly formed of Al is possible, thereby reducing the
number of processes as compared with the other amorphous alloys. At this
time, the content of Al is preferably 15 at % or more for stabilizing
amorphous state. The content is more preferably 15 to 80 at % to maintain
the surface energy of the amorphous thin film to be high. Examples of such
Al amorphous alloys are Ta.sub.x Al.sub.1-x (0.20.ltoreq.x.ltoreq.0.85),
Nb.sub.x Al.sub.1-x (0.20.ltoreq.x.ltoreq.0.85), V.sub.x Al.sub.1-x
(0.20.ltoreq.x.ltoreq.0.60), W.sub.x Al.sub.1-x
(0.15.ltoreq.x.ltoreq.0.50) and Mo.sub.x Al.sub.1-x
(0.25.ltoreq.x.ltoreq.0.80). Further, since Cu amorphous alloys have
excellent contact properties with metal wiring mainly made of Cu, a
contact part with the high reliability can be provided. Examples of such
Cu amorphous alloys are Ti.sub.x Cu.sub.1-x (0.18.ltoreq.x.ltoreq.0.70),
Zr.sub.x Cu.sub.1-x (0.18.ltoreq.x.ltoreq.0.70), Hf.sub.x Cu.sub.1-x
(0.20.ltoreq.x.ltoreq.0.70), Y.sub.x Cu.sub.1-x
(0.10.ltoreq.x.ltoreq.0.53) and Ta.sub.x Cu.sub.1-x
(0.20.ltoreq.x.ltoreq.0.80). Especially for metal wiring mainly made of Cu
where required electrical resistance is as low as bulk material, amorphous
alloys such as V.sub.x Co.sub.1-x (0.15.ltoreq.x.ltoreq.0.80), Nb.sub.x
Cr.sub.1-x (0.25.ltoreq.x.ltoreq.0.45), Nb.sub.x Co.sub.1-x
(0.22.ltoreq.x.ltoreq.0.55), Ta.sub.x Cr.sub.1-x
(0.25.ltoreq.x.ltoreq.0.40), Ta.sub.x Co.sub.1-x
(0.25.ltoreq.x.ltoreq.0.45), Cr.sub.x Co.sub.1-x
(0.50.ltoreq.x.ltoreq.0.70), Mo.sub.x Co.sub.1-x
(0.20.ltoreq.x.ltoreq.0.60), and W.sub.x Co.sub.100-x
(0.20.ltoreq.x.ltoreq.0.60) are also preferably used since they do not
form solid solution, and can avoid the inherent electrical resistance
increase by interfacial reaction at elevated temperature for sintering. In
these amorphous alloys, if a so-called metalloid element such as Si, Ge, P
or B is contained, the stability of being amorphous can be further
enhanced. Moreover, an amorphous thin film may be of multi-layer structure
where different amorphous materials are laminated. At this time, the upper
most surface is preferably formed of the above-mentioned amorphous alloys
with the high surface energy; and SiO.sub.2, polyimide, TEOS, SiN and the
like containing B or P may be used as the underlying layer of the above
multi-layer structure.
The above-mentioned metal wiring, which is formed on an amorphous thin
film, is formed of crystal with the high orientation and crystalline
properties which is oriented in a given plane direction. In the case of
highly oriented crystal, the angle formed between the normal line
direction of the close-packed plane of each crystal grain and the normal
line direction of the bottom surface of metal wiring is preferably
80.degree. or less. In the case where metal wiring is of single crystal,
the angle between the close-packed plane and the wiring longitudinal
direction is preferably 20.degree. or less. At this time, metal wiring is
formed such that a (111) plane of the close-packed plane in the case where
metal wiring crystal structure is fcc structure; a (110) plane in the case
of bcc structure; or a (0001) plane in the case of hexagonal structure is
approximately parallel to the wiring longitudinal direction. Moreover,
taking into account the degree of freedom in wiring design, the
close-packed plane is preferably an upper plane, that is, metal wiring
oriented in the close-packed plane is preferably formed.
In the present invention, metal wiring is preferably of highly oriented
crystal where small angle boundary energies are distributed, which small
angle boundary energies are 88% or less of general random grain boundary
energies in polycrystal where general random grain boundary energy is
defined by one third of the surface energy of a solid. Examples of such
small angle boundaries with low grain boundary energy are small angle
boundaries with a relative misorientation of 10.degree. or less in tilt,
rotation and combination thereof around orientation axes of neighboring
crystal grains, coincidence boundaries where the .SIGMA. value of grain
boundaries is 10 or less, and grain boundaries with a relative
misorientation of 3.degree. or less from a coincidence boundary. The
number of such small angle boundaries are preferably half or more of
entire grain boundaries, more preferably 90% or more. Existence of such
small angle boundaries results in that a site where voids form due to
stress-migration is intentionally provided in metal wiring, a void volume
is suppressed because of large surface energy increase with void growth at
a grain boundary with low energy, and metal wiring failure is prevented.
Thus, such metal wiring of highly oriented crystal has the excellent
reliability even without an under amorphous thin film.
This metal wiring can be used not only in a single-layer wiring but also in
multi-layer wirings and a conductive connecting part in the longitudinal
direction thereof, namely, a via or through hole. Even if a material of
the conductive connecting part in the longitudinal direction is different
from that of a wiring layer above or under the part, continuity of the
crystalline orientation of the metal wiring can be maintained, thus
allowing the improved reliability. Further, this metal wiring may be of
multi-layer structure where different kinds of metals or metals with
different crystal states or conductive materials are laminated.
Illustrative materials for such metal wirings have the low electric
resistance, and are fcc structured pure Al, pure Cu, pure Au, pure Ag,
Al--Cu, Al--Ti, Al--Cr, Al--Ta, Al--Mg, Al--In, Al--Li, Cu--Be, Cu--Ag,
Au--Pt, Au--Ag, Au--Pd, Au--Cu, bcc structured pure W. In the case of an
alloy, the amount of addition of a solute is desirably in the range
allowing a complete solid solution. In this case, Si may be contained in 1
wt % or less. Making an alloy can reduce the surface energy of metal
wiring (surface energy of a deposited material .gamma.f).
Such metal wiring may contain an element in the grain boundaries, or an
upper or lower layer thereof, which element has a melting point lower than
that of a wiring material, which does not form an intermetallic compound
with an element forming the metal wiring, and whose affinity with a
substrate or interposed layer is smaller than that of an element forming
the metal wiring. For example, in the case of using Al or an Al alloy for
metal wiring, at least one element of Ga, In, Cd, Bi, Pb, Sn and Tl is
exemplified. In the case of using Cu or a Cu alloy for metal wiring, at
least one element of Pb and Tl is exemplified.
Metals with a high melting point or silicides, nitrides, oxides or carbides
of metals with a high melting point may coat on the metal wiring.
Electronic parts thus constructed of the invention are manufactured in the
following manner.
First, if necessary, an insulative layer, a barrier layer, a contact layer
and the like are formed on a substrate. Thereafter, an amorphous thin film
is formed by conventional deposition methods such as a sputter method so
as to match with a spacing of a particular crystalline plane of metal
wiring to be formed thereon. Subsequently, while keeping vacuum, the metal
wiring is formed. If the amorphous thin film is exposed to the air, the
surface is cleaned by Ar bias sputtering and the like, and then the metal
wiring is formed. However, in the case where an amorphous thin film
contains B, C, N, or the like and the high surface energy state of the
amorphous thin film is maintained at an oxygen or nitrogen atmosphere, an
oxide layer is hardly formed on the surface, even if the amorphous thin
film is exposed to the air. Thus, metal wiring may be formed without
surface cleaning. In the formation of metal wiring, desirable methods for
forming a metal thin film by physical vapor deposition include a sputter
method, bias sputter method and ion beam method. Desirable methods for
forming a metal thin film by chemical vapor deposition include, for
example in the case of an Al-CVD method, a thermal chemical vapor
deposition (CVD) method with the use of alkylaluminum such as TIBA or
alkylaluminum hydride such as DMAH as a source gas. In these methods, for
example, Si or Cu may be contained in the source gas during film
deposition. An alloy may be made by lamination by ion implantation or
sputtering, and subsequent heat treatment after film deposition.
Further, an amorphous thin film and metal wiring may be formed thereon via
an insulative layer and the like to construct multi-layer wirings.
After the film deposition, heat treatment may be conducted so that crystal
can grow from seeds. In the case where seeds are Si, the following two
pretreatment are preferable. One pretreatment contains a diluted-HF
treatment step and thereafter, without a water rinse, a drying step in
N.sub.2 with a dew point of -90.degree. C. or less. Another pretreatment
contains a diluted-HF treatment step, a washing step with ultra pure water
where dissolved oxygen concentration is 10 ppb or less, and thereafter a
drying step in N.sub.2 with a dew point of -90.degree. C. or less.
Further, a graphoepitaxy method may be used with processing the surface of
the substrate. It is previously described that crystal of a metal thin
film formed on an amorphous thin film of an underlying layer with the high
surface energy has the extremely high orientation, and is oriented in a
given plane direction. It appears that if the surface energy of the under
layer is high, a wetting angle of nucleuses vapor-deposited is small and
thereby, for example in the case of Al, a (111) plane with low surface
energy can stably grow. However, at this time, directions in a plane of
the growing nucleuses are at random. Thus, control of directions in a
plane is required for the higher wiring reliability. According to the
invention, an amorphous thin film with grooves formed thereon is used as
an underlying layer, and thereby not only the crystalline properties of a
metal thin film to be formed but also control of directions in a plane are
sufficiently enhanced. In the amorphous thin film, the bottom part of the
grooves may be made of a material different from or identical to that of
which the side wall part is made. However, it is preferable that the
bottom part and side wall part of the grooves are made of different
materials and difference therebetween in the surface energy is utilized at
the time of forming a metal thin film. The reasons therefor are as
follows; A material to be deposited orientates and grows in a part with
higher surface energy than the bottom or side wall part with lower surface
energy. At the same time, direction of the other axis of deposited film
can be controlled at an interface with the other low-surface-energy part.
As a result, a metal thin film similar to single crystal can be formed.
Further, in this case, even if an amorphous thin film is subjected to
thermal treatment to be crystallized before or after the deposition of a
metal thin film, a metal thin film with the high crystalline properties
can be obtained.
Desirable grooves are as follows: The shape of the grooves is a stripe,
rectangle, square, regular triangle or combination thereof. Many of such
grooves are arranged such that one side of the groove is parallel to one
of the other groove with accuracy of .+-.5.degree.. The width of each
groove is the average grain size of metal wiring or less and the space of
each groove is also the average grain size of metal wiring or less. In the
case of stripe-like grooves, the groove width and space are preferably the
average grain size of metal wiring or less. Though an underlayer to form
the amorphous thin film does not particularly be subject to restriction,
it is preferable that the surface of the underlayer, is smooth. If there
are fine undulations thereon, the amorphous thin film keep an uneven
surface of the underlayer, and the direction of orientation in the metal
wiring falls into disorder. Thus, the crystal properties of the metal
wiring are degraded. To solve the above problem, it is desirable to
flatten the surface of the underlayer prior to forming the amorphous thin
film or the surface of the amorphous thin film after forming the amorphous
thin film. As methods for flattening the underlayer, polishing, etching,
melt-flowing and the likes are given as examples. And as methods for
flattening the amorphous thin film, polishing and etching and the likes
are given as examples.
When forming metal wiring on an amorphous thin film, it is important that a
surface oxide is not formed on the amorphous thin film, as described
above. Further, it is a matter of course that when the metal wiring is
continuously formed without exposing the amorphous thin film in an air
after forming, the formation of a surface oxide film on the amorphous thin
film is affected by a base pressure before and after forming the amorphous
thin film. Accordingly, it is important to maintain the base pressure to
be 1.times.10.sup.-6 Torr or less. To be concrete, it is necessary to
maintain the base pressure of around 1.times.10.sup.-7 Torr or
1.times.10.sup.-8 Torr. A preferable method for removing a surface oxide
of the amorphous thin film is plasma etching immediately before the
deposition of a metal thin film. After etching, it is important to
maintain the vacuum to be 1.times.10.sup.-6 Torr or less. A CVD method or
PVD method may be applied as a method for forming a metal thin film. A
substrate temperature is preferably raised to promote migration of
deposited particles by means such as resistance heating, electron beam
irradiation and laser beam irradiation. Further, an oblique vapor
deposition method, where a vapor deposited particle flux is oblique
against a substrate, is preferable.
Further, in the case where a conductor layer formed of Al or an Al alloy,
or Cu or a Cu alloy is deposited to form a metal thin film, the above
metal wiring of highly oriented crystal can be obtained by supplying an
element with the low surface energy before or during the deposition of the
conductor layer.
Concretely, in the case of forming a metal wiring consisted of Al or Al
alloy, one or two elements selected from the group of Ga, In, Cd, Bi, Pb,
Sn and Tl are supplied. In the case of forming a metal wiring consisted of
Cu or Cu alloy, one or two elements selected from the group of Pb and Tl
are supplied. Referring to FIG. 1, when such elements are supplied to form
a control layer consisting of at least one atomic layer, the relationship
between .gamma.f and .gamma.i will be considered. In FIG. 1, reference
number 1 is a substrate, 5 an insulative layer formed of a thermal oxide
film, 50 a control layer, 2 metal wiring. In this case, since the surface
energy of an element forming the control layer is low, the sum of .gamma.f
and .gamma.i in the (b) state is smaller than that in the (a) state. Thus,
when such elements are supplied on a substrate and a conductor layer
destined for a metal wiring is deposited, the elements diffuse towards the
surface of the conductor layer to minimize the free energy. As a result,
the surface energy of the deposited substrate seemingly decreases and its
film growth becomes similar to layer growth. Accordingly even if an
underlying material is one of an insulative layer, barrier layer, contact
layer and amorphous thin film layer, a metal thin film with the high
crystalline properties can be formed. This effect is remarkable when the
above elements are supplied during the deposition of the conductor layer.
The sufficient supplying amount of the elements is half or more atomic
layer. The supply of the elements promotes the surface diffusion of the
deposited material to attain large grain size of crystals, too. This will
be described referring to FIG. 29 in detail. FIG. 29(a) is a surface SEM
photograph when Al was vapor deposited in a thickness of 500 .ANG. on a
SiO.sub.2 insulative layer. FIG. 29(b) is a surface SEM photograph when Bi
of 1 atomic layer was supplied at the time of Al vapor deposition. In the
case where Bi is not supplied, a substrate is subjected to thermal
treatment at 400.degree. C. for 3 hours under vacuum, thereby obtaining
film aggregation. However, as shown in the drawings, if Bi is supplied
during deposition of a conductor layer, film aggregation can be obtained
without heating a substrate immediately after the deposition.
In the case where a barrier layer, contact layer or the like, which is made
of a compound or an alloy, is formed as an underlying layer on a
substrate, subjected to thermal treatment, and a conductor layer is then
deposited; the underlying layer is etched by plasma containing at least
one element constituting the compound or alloy as a pretreatment for the
deposition of the conductor layer, thereby allowing the formation of a
metal thin film with the high crystalline properties and orientation. This
is because the etching prevents oxidation of the surface of the underlying
layer made of the compound and alloy, and active seeds on the surface so
that a stable interface can be formed. For example, in the case where the
underlying layer is formed of nitride, preferably the surface is etched by
plasma of a mixture of an inert gas and nitrogen and a conductor layer is
then deposited thereon. At this time, preferably the conductor film is
deposited continuously after etching under vacuum. However, exposure to
the air for a short period of time is allowable. Regarding the etching,
after etching with the use of a mixture gas, this may be exposed to plasma
containing only elements constituting the compound and alloy. These
etching are preferably performed while supplying a bias voltage to a
substrate. The desirable voltage is -100V or less. Thereafter,
illustrative methods for depositing a conductor layer are various CVD
methods as well as physical vapor deposition methods such as a sputtering
method and resistance heating vapor deposition method. Illustrative
materials of which the conductor layer is formed are Si, WSi, MoSi, pure
Al, an Al alloy, pure Cu, a Cu alloy, W, Au, and Ag. Desirable Al alloys
are an Al--Cu alloy, Al--Cr alloy and Al--Mg alloy. Alternatively, these
materials may be layer-like laminated.
For example, in the case of an Al-CVD method, film-deposition is preferably
performed by a thermal CVD method with the use of alkylaluminum such as
TIBA or alkylaluminum hydride such as DMAH as a source gas. At this time,
Si or Cu may be contained in the source gas during film deposition. An
alloy may be made by lamination by ion implantation or sputtering, and
subsequent thermal treatment after film deposition.
The improvement in the crystalline properties of a metal thin film thus
obtained allows electronic parts with metal wiring having the excellent
reliability such as the high stress-migration and electromigration
endurance.
Moreover, an electrical current is loaded in metal wiring via an insulative
layer and the like on a substrate after the formation of metal wiring.
This improves the stressmigration endurance of the metal wiring and
suppresses occurrence of thermal etch pits. This current loading allows
similar effects in the case where an amorphous thin film is not formed or
the other film is interposed. However, in the case where grain boundaries
in the metal wiring consists of small angle boundaries and twin boundaries
with low grain boundary energy, the more remarkable effect derived from
such current loading is obtained. Here, it is also preferable to form
metal wiring of highly oriented crystal where the previously described
small angle boundaries with the low grain boundary energy are distributed.
Because such small angle boundaries become moveable and are easily emitted
out from metal wiring, and approaches single-crystalline by a current
loading. A current density ranged from 5.times.10.sup.6 A/cm.sup.2 to
2.times.10.sup.7 A/cm.sup.2 is preferable.
A reason for limiting a current density is as follows. If a current density
is 5.times.10.sup.6 A/cm.sup.2 or less, the abovedescribed effect by
current loading cannot be obtained. If a current density is
2.times.10.sup.7 A/cm.sup.2 or more, an electromigration-induced void is
formed due to an increased atomic flux divergence from temperature
inhomogeneity by enhanced Joule-heating, resulting in a worse wiring shape
and poor reliability. A proper loading period depends on the length and
shape of metal wiring. However, in view of the stability of Joule-heating
and dislocation emission speed, 1 minute or longer is preferable. A
substrate temperature may be room temperatures or raised temperatures,
preferably 300.degree. C. or lower. If a substrate is heated to
300.degree. C. or higher, thermal etch pits may take place.
In the case of multi-layer wirings, current-loading is preferably conducted
at every time of forming metal wiring. However, current loading may be
conducted simultaneously in two or more metal wirings. In this case,
materials similar to metal wiring are preferably used for filling a via
part (conductive connecting part). However, difference in the amount of
additives is allowed as far as the difference is 10% or less per total
amount of additives.
According to the present invention, as mentioned above, after an amorphous
thin film and metal wiring are successively formed on a substrate to
produce an electronic part of the invention, a given thermal treatment may
be conducted for the purpose of further crystal grain growth in metal
wiring of highly orientated crystal. At this time, the amorphous thin film
is allowed to be crystallized or disappear by the thermal treatment. Since
its crystalline property is improved by the crystal grain growth of the
highly orientated crystal, the reliability of the metal wiring can be
further improved.
Further, although the present invention relates to the improvement in the
reliability of metal wiring as mentioned above, the technique of the
invention can be similarly applied to an electrode part of a capacitor or
resistance heater in an electronic part.
For example, in the case of forming an under electrode of a capacitor, if
an interatomic distance corresponding to a peak of halo pattern appearing
in diffraction measurement of an amorphous thin film of an underlying
layer approximately matches with a spacing of a particular crystal plane
including atoms with the first adjacent interatomic distance of the under
electrode, the interface energy between the amorphous thin film and under
electrode is reduced so that the under electrode with the very excellent
crystalline properties can be formed. Accordingly, the crystalline
properties of a dielectric thin film formed thereon is enhanced.
If an amorphous thin film is used as a resistance heater uniform and stable
electrical resistance can be attained. Further if an electrode is
deposited on this amorphous thin film such that the interatomic distance
of the amorphous thin film approximately matches with the spacing of the
electrode, the crystalline properties of the electrode are improved and
electromigration induced degradation is suppressed at the time of a large
current application.
Moreover, according to the present invention, a pad part connecting with
metal wiring is formed of single crystal or highly orientated crystal with
the previously mentioned small angle boundaries having the low grain
boundary energy, like the metal wiring. At the same time, the shape of the
pad part is an aggregation of fine lines successively branched from the
metal wiring. As a result, the reliability of the pad part can be
enhanced. Here, "successive branch" means, as shown in FIG. 4, that fine
line increases in a branch-shape in the upper and lower directions of
metal wiring assumed as a central axis. The number of upper branches may
not be the same as that of lower branches. The branch may not be
perpendicular to the metal wiring. The preferable angle .theta. is
90.degree. or less. As a result, voids at the upper side of the wiring,
which form and move in the wiring, successively move to fine lines above
the pad part, whereas voids at the lower side of the wiring, which form
and move in the wiring, successively move to fine lines under the pad
part. The voids cannot grow in the wiring width or more, and remain in
fine lines around the outer periphery of the pad. If an element
constituting fine lines run out by voids in the fine line of the mostly
outer periphery, the voids remain in the next fine line. A central part of
the pad part bonded with wire connected to an external power source does
not allow the defect to be accumulated, thereby extremely enlarge the
lifetime of the pad part.
The structure where branch successively advances prevents rapid change of a
current density in a connecting part with metal wiring, allowing
attemperment of flux divergence due to change in a current density. Thus,
not only voids in a (-) pad but also hillocks in a (+) pad are
advantageously dispersed. Spacing between branches is not required to be
equal.
The branched fine lines are preferably connected with a fine line running
in the perpendicular direction. Further, the width of these fine lines is
preferably more than that of metal wiring.
Moreover, it is effective for a pad part that a region where a current
density is one tenth or more of metal wiring is made of an aggregation of
fine lines. In a region where a current density is one tenth or less, a
continuous (not-branched) pad is allowable.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1(a) and (b) are sectional views for explaining functions of the
invention.
FIG. 2 is a sectional view showing a layer-structure of the invention.
FIGS. 3(a) to (d) are sectional views showing metal wiring structure of the
invention.
FIG. 4 is an enlarged view showing pads of the invention.
FIG. 5 is a view showing a multi-target sputter apparatus or use in the
invention.
FIG. 6 is a sectional view according to Example 1.
FIG. 7 is a sectional view according to Example 3.
FIG. 8 is a sectional view according to Example 5.
FIG. 9 is a sectional view according to Example 6.
FIG. 10 is a sectional view according to Example 7.
FIG. 11 is a sectional view according to Example 8.
FIGS. 12(a) to (f) are sectional view showing a method for forming a wiring
according to Example 9.
FIG. 13 is a view showing results of an accelerated test according to
Example 9.
FIG. 14 is a sectional view according to Example 10.
FIG. 15 is a plan view showing a test substrate with a wiring part
according to Example 11.
FIG. 16 is a sectional view according to Example 14.
FIG. 17 is a sectional view according to Example 16.
FIG. 18 is a sectional view according to Example 17.
FIG. 19 is a sectional view according to Example 18.
FIG. 20 is a sectional view according to Example 19.
FIGS. 21(a) to (g) are sectional views according to Example 21.
FIG. 22 is a sectional view according to Example 21.
FIGS. 23(a) to (e) are sectional views showing a flow of steps according to
Example 23.
FIG. 24 is a sectional view according to Example 25.
FIG. 25 is a sectional view according to Example 27.
FIGS. 26(a) and (b) are RHEED photographs according to Example 30.
FIG. 27 is a sectional view according to Example 38.
FIG. 28 is a sectional view according to Example 43 and Example 44.
FIGS. 29(a) and (b) are SEM photographs according to Example 46.
FIGS. 30(a) to (d) are views according to Example 48.
FIG. 31 is a view showing a four-terminal pattern according to Example 54.
FIG. 32 is a sectional view according to Example 57.
FIG. 33 is a sectional view according to Example 59.
FIG. 34 is a sectional view showing an example of a wiring part of an
active matrix type liquid crystal display apparatus according to the
invention.
FIG. 35 is a view showing a pattern for measuring the resistivity of
samples according to Example 60.
FIG. 36 is a typical view showing crystal structures of the metal wiring
and to explain the first-nearest interatomic distance thereof.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of the present invention will be described in more detail.
EXAMPLE 1
Referring to FIGS. 5 and 6, an embodiment will be described.
Using a six-inch silicon wafer substrate 1 with a 4000 .ANG. insulative
layer 5 of a thermal oxide film (SiO.sub.2), an amorphous thin film 3 and
metal wiring 2 were successively formed by sputtering. First, an AlTa film
was formed as an amorphous thin film 3 by means of a multi-target sputter
apparatus as shown in FIG. 5. The sputtering conditions are shown below.
In FIG. 5, reference numeral 8 indicates a high frequency power source, 9
a matching circuit, 10 a mass flow controller, 11 a target.
Sputter system: RF magnetron system
Target: 100 mm.phi. AlTa mosaic target (concentric circle like form)
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 0.20 Pa
Applied power: 10 W/cm.sup.2
Film thickness: 500 .ANG.
Composition analysis revealed that the formed film was Al.sub.40 Ta.sub.60
(hereinafter, numeral value shows ratio of an atomic composition). X-ray
diffraction revealed that the film was amorphous and that an interatomic
distance ds corresponding to peak of halo pattern was 2.34 .ANG.. The
following fact was found. Namely, since a spacing df of Al (111) was 2.34
.ANG., the relation, .vertline.df-ds.vertline./ds=0 was satisfied. Thus,
if the amorphous thin film contains an element mainly forming metal wiring
and has an appreciate composition, the spacing ds can match with the
spacing of a particular crystal plane of the metal wiring. In this
embodiment, a mosaic target was used. However, other methods such as
simultaneous sputtering with the use of a binary target and lamination of
each element could produce a similar amorphous thin film.
Next, keeping vacuum, Al was sputtered on the Al.sub.40 Ta.sub.60 film. The
sputtering conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Al target
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 1 Pa
Applied power: 5 W/cm.sup.2
Film thickness: 4000 .ANG.
The Al film thus formed was evaluated for the orientation and crystalline
properties by X-ray diffraction. The full width of half-maximum
(hereinafter referred to as FWHM) of a (111) rocking curve (orientation
FWHM) was 1.2.degree. and bragg reflection other than (hhh) reflection,
for example (200), (220) or the like, was not observed.
The film thus formed with a layer-structure shown in FIG. 6 was processed
into a four-terminal pattern 0.5 .mu.m in width and 1 mm in length, and
subjected to an electromigration (EM) test. The test conditions were that
a wiring temperature was 200.degree. C. and a current density was
2.times.10.sup.6 A/cm.sup.2. As a result of the test, it was confirmed
that even after an elapsed time of 1000 hours there was no failure and
excellent reliability was obtained. When the electric resistance increased
by 10% of a value just after the test starts in the EM test, it was judged
that wiring failure took place. This judgement was the same in the
following examples.
Similarly, various combinations of an amorphous thin film and metal wiring
(an amorphous thin film/metal wiring); that is, (Pt.sub.21 Zr.sub.79 /Pt),
(Cu.sub.50 Ti.sub.50 /Cu), (Ag.sub.55 Cu.sub.45 /Ag), and (Fe.sub.80
B.sub.20 /Fe); were formed. Similar evaluation of the orientation FWHM
revealed that Pt, Cu and Ag were (111) orientation and the FWHMs thereof
were 1.4.degree., 1.8.degree. and 1.6.degree. respectively; and Fe was
(110) orientation and the orientation FWHM of (110) reflection thereof was
1.7.degree..
EXAMPLE 2
Like Example 1, an amorphous thin film made of Ni.sub.30 Ta.sub.70 (melting
point of intermetallic compound of Ni.sub.30 Ta.sub.70 : 1500.degree. C.)
was formed and a metal wiring made of Al (melting point: 660.degree. C.)
was formed thereon. Namely, the amorphous thin film contained an element
which has a melting point higher than that of a metal wiring and which
could constitute an intermetallic compound with a main element forming the
metal wiring. Here, an interatomic distance ds of Ni.sub.30 Ta.sub.70
corresponding to a peak of halo pattern was 2.33 .ANG.. This approximately
matches with a spacing df 2.34 .ANG. of Al (111). As a result of
evaluation similar to Example 1, (111) orientation FWHM of 0.9.degree. and
excellent crystalline properties were observed. Further, in the EM test,
it was confirmed that even after an elapsed time of 1000 hours there was
no failure and excellent reliability was also obtained.
Similarly, various combinations of an amorphous thin film and metal wiring
(an amorphous thin film/metal wiring); that is, (Pd.sub.80 Si.sub.20 /Al),
(Ag.sub.55 Cu.sub.45 /Al), and (W.sub.70 Zr.sub.30 /Al); were formed.
Similar evaluation revealed that the (111) orientation FWHMs thereof were
1.9.degree., 1.8.degree. and 1.2 respectively.
EXAMPLE 3
Like Example 1, an amorphous thin film made of a Co-based alloy, Co.sub.80
Zr.sub.9 Nb.sub.11 was formed and a metal wiring made of Al was formed
thereon. Here, an interatomic distance ds of Co.sub.80 Zr.sub.9 Nb.sub.11
corresponding to a peak of halo pattern was 2.04 .ANG.. This approximately
matches with a spacing df 2.02 .ANG. of Al (200). As a result of
evaluation similar to Example 1, (111) orientation and excellent
crystalline properties were observed. Further, in the EM test, it was
confirmed that even after an elapsed time of 1000 hours there was no
failure and excellent reliability was obtained.
Similarly, various combinations of an amorphous thin film and metal wiring
(an amorphous thin film/metal wiring); that is, (Co.sub.80 Zr.sub.8
Nb.sub.12 /Al), (Co.sub.85 Zr.sub.6 Nb.sub.9 /Al), (Co.sub.88 Zr.sub.8
Ta.sub.9 /Al), and (Co.sub.90 Hf.sub.6 Pd.sub.4 /Al); were formed. Similar
evaluation revealed that the (111) orientation FWHMs thereof were
1.2.degree. and satisfactory crystalline properties was obtained.
As shown in FIG. 7, Al metal wirings 2 were formed after various
combinations of the following steps; these steps were that a
polycrystalline TiN/Ti layer was formed on the insulative layer 5 as a
barrier layer 6, that an amorphous thin film 3 (Co.sub.80 Zr.sub.9
Nb.sub.11) was formed thereon, that thereafter it was exposed to the air
as shown in Table 1, and that it was then subjected to Ar bias sputtering.
The crystalline orientation of these Al metal wirings were evaluated with
the FWHM of an Al(111) rocking curve by X-ray diffraction using a
CuK.alpha. line. As shown in Table 1, in the cases of no amorphous thin
film and no Ar bias sputtering after exposure to the air, the crystalline
orientation was remarkably degraded.
TABLE 1
______________________________________
Surface treatment
FWHM of a
Underlying material
Ex- (111) rocking
SiO.sub.2
TiN/Ti Amorphous posure
Ar bias
curve of metal
layer layer thin film to air
sputtering
wiring
______________________________________
1 .largecircle.
-- .largecircle.
-- -- 1.2.degree.
2 .largecircle.
.largecircle.
.largecircle.
-- -- 1.2.degree.
3 .largecircle.
-- -- -- -- 8.degree. or more
4 .largecircle.
.largecircle.
-- -- -- 4.degree.
5 .largecircle.
-- .largecircle.
.largecircle.
.largecircle.
1.3.degree.
6 .largecircle.
.largecircle.
.largecircle.
.largecircle.
.largecircle.
1.3.degree.
7 .largecircle.
-- .largecircle.
.largecircle.
-- 8.degree.
8 .largecircle.
.largecircle.
.largecircle.
.largecircle.
-- 8.degree.
9 -- .largecircle.
.largecircle.
-- -- 1.2.degree.
______________________________________
.largecircle.: Yes (existent or conducted),
--: No (nonexistent or nonconducted)
EXAMPLE 4
Like Example 1, amorphous thin films and metal wirings shown in Table 2
were formed. As also shown in Table 2, in this embodiment, amorphous thin
films with larger surface energy than that of metal wiring in the
crystalline state were used.
TABLE 2
__________________________________________________________________________
Amorphous thin film Metal wiring FWHM of a (111)
Interatomic
Surface energy
Spacing
Surface energy
rocking curve
Composition
distance ds (.ANG.)
(erg/cm.sup.2)
Composition
df (.ANG.)
(erg/cm.sup.2)
.vertline.df - ds.vertline./ds
of metal wiring
__________________________________________________________________________
1 Ni.sub.62 Nb.sub.38
2.11 1826 Al (200)2.02
866 0.04 1.1.degree.
2 Ni.sub.30 Zr.sub.70
2.51 1570 Al (111)2.34
866 0.07 1.2.degree.
3 TiB.sub.2
2.01 1698 Al (200)2.02
866 0.005
1.8.degree.
* SiO.sub.2
4.78 605 Al (111)2.34
866 0.51 8.2.degree.
__________________________________________________________________________
*: Comparative Example
In each case, a spacing ds corresponding to a peak of halo pattern in the
amorphous thin film approximately matches with a lattice distance df of
Al. As a result of evaluation similar to Example 1, (111) orientation and
excellent crystalline properties were obtained, as shown in Table 2.
Further, in the EM test, it was confirmed that even after an elapsed time
of 1000 hours there was no failure and excellent reliability was obtained.
For example, borides, carbides and nitrides of TiB.sub.2 and the like were
preferably used as an amorphous thin film, since their surface energy was
large. The surface energy is represented by the following approximation
equation;
.DELTA.E.sup.SV =Y.lambda..sup.2 /4 .pi..sup.2 X.sub.0
.DELTA.E.sup.SV : surface energy
Y: Young's module
.lambda.: distance between atoms where force reaches (X.sub.0 is an
approximate value)
X.sub.0 : distance between atoms
At the same time, as a comparative example, a metal wiring was directly
formed on SiO.sub.2 in a similar way to Example 1. An interatomic distance
ds of SiO.sub.2 corresponding to a peak of halo pattern does not
approximately match even for the nearest spacing df of (111) Al. Further,
the surface energy of SiO.sub.2 is smaller than that of Al. As a result of
evaluation similar to Example 1, the (111) orientation FWHM was as large
as 8.2.degree. and in the EM test a wiring failure was observed within 10
hours.
EXAMPLE 5
Referring to FIG. 8, an embodiment will be described.
In this example, as shown in FIG. 8, a conductive connecting part 4, namely
a via, was formed in the longitudinal direction. Concretely, first, a
SiO.sub.2 thermal oxide film was formed as an insulative layer 5 on a Si
substrate 1 and thereafter a 4000 .ANG. thick thin film, which was made of
Al, Cu, W or MoSi.sub.2, was deposited as a under-layer metal wiring 2'.
On this thin film, a 3000 .ANG. thick SiO.sub.2 interlayer insulative film
5' was deposited by means of a thermal CVD method. In this interlayer
insulative film 5', a via (or through hole) 4 with a diameter of 50 .mu.m
was formed by means of conventional PEP, reactive ion etching (RIE) steps.
Next, the via 4 was filled with W by a selective CVD method. After leveling
by etchback, a 200 .ANG. thick Co.sub.80 Zr.sub.9 Nb.sub.11 thin film was
formed as an amorphous thin film 3 of the present invention. Subsequently,
if the surface of Co.sub.80 Zr.sub.9 Nb.sub.11 was exposed to the air one
time, it was subjected to Ar RF plasma cleaning. Then pure Al thin film
was deposited as a metal wiring 2 in a thickness of 4000 .ANG. by
sputtering. The crystalline orientation of the Al thin film was evaluated
with the FWHM of an Al (111) rocking curve by X-ray diffraction using a
CuK.alpha. line. An incident X-ray was diaphragmed to .phi.50 .mu.m by a
collimator to examine change and distribution of FWHM near the via. As a
result, FWHM did not change dependent on positions and was uniformly
1.3.degree., thereby exhibiting the excellent crystalline properties.
EXAMPLE 6
Referring to FIG. 9, an embodiment will be described.
Like Example 5, a via 4 was formed and then, as shown in FIG. 9, Ni.sub.62
Nb.sub.38 was formed in a thickness of 300 .ANG. as an amorphous thin film
3 by sputtering. As a result, as shown in FIG. 9, although a side wall of
the via become slightly thin, a Ni--Nb layer was conformably formed. Under
vacuum of 1.times.10.sup.-7 Torr, a 4000 .ANG. thick pure Al thin film was
continuously formed as a metal wiring 2 thereon by sputtering. As a result
of evaluation similar to Example 5, FWHM was uniformly 1.35.degree..
EXAMPLE 7
Referring to FIG. 10, an embodiment will be described.
Like Example 5, a via 4 was formed and then, as shown in FIG. 10, Al.sub.40
Ta.sub.60 was formed as an amorphous thin film 3 by sputtering. At this
time, provision of a collimator between a substrate with the via and
target improved the direct-advance property of particles to be deposited.
Accordingly, an amorphous layer was hardly formed on a side wall of the
via 4 and a 100 .ANG. Al--Ta amorphous thin film 3 could be formed on the
bottom surface of the via 4 and interlayer insulative film 5'. After
exposure to the air one time, it was subjected to Ar RF bias sputter
cleaning. Then pure Al thin film was deposited in a thickness of 4000
.ANG. as a metal wiring 2 by sputtering. As a result of evaluation similar
to Example 5, FWHM was uniformly 1.1.degree..
EXAMPLE 8
Referring to FIG. 11, an embodiment will be described.
As shown in FIG. 11, first, an Al.sub.40 Nb.sub.60 film was formed as an
amorphous thin film 3' on an insulative layer 5 formed of a SiO.sub.2
thermal oxide film, and thereafter under vacuum of 1.times.10.sup.-7 ;
Torr or less pure Al was continuously deposited to form an under-layer
metal wiring 2' with a thickness of 4000 .ANG.. The FWHM of a rocking
curve of the under-layer metal wiring 2' was 1.2.degree.. Like Example 5,
a SiO.sub.2 interlayer insulative film 5' and via 4 were formed on the Al
under-layer metal wiring 2'. Next, the via 4 was selectively filled with
Al by means of a thermal CVD method using TIBA (triisobuthyl aluminum,
i-(C.sub.4 H.sub.9).sub.3 Al) as a source gas. This Al with which the via
4 was filled had the continuous crystalline orientation of the lower Al
and had the same FWHM of a rocking curve as that of the under-layer metal
wiring 2'. Subsequently Al--Nb was continuously deposited in a thickness
of 250 .ANG. as an amorphous thin film 3 by sputtering. After this had
been exposed to the air and then subjected to bias cleaning by Ar RF
plasma, an Al film was deposited in a thickness of 250 .ANG. as a metal
wiring 2 by means of a sputter or thermal CVD method using TIBA. The
distribution of the crystalline orientation of this Al film was uniform
and the rocking FWHM was 1.2.degree.. Further, Al may be deposited after
removing an amorphous thin film 3 corresponding to the via 4 by a
conventional PEP step and ion-milling step. Even the Al film thus obtained
had the uniform orientation including the via part, and the FWHM was
similarly 1.2.degree..
On the other hand, in a comparative example, an amorphous thin film did not
exist. According to this comparative example, in the both cases, the FWHM
of Al on amorphous SiO.sub.2 was about 8.degree. and the uniformity in
orientation thereof was not satisfactory, especially the orientation of
the via part being considerably disturbed.
EXAMPLE 9
Referring to FIGS. 12 and 13, an embodiment will be described.
As shown in FIG. 12(a), an insulative layer formed of amorphous SiO.sub.2
was formed on the surface of a Si substrate 1. First, a 1000 .ANG. thick
amorphous thin film 3 was deposited on the amorphous SiO.sub.2 by a
sputter method (FIG. 12(b)) and then the amorphous thin film 3 on parts
other than parts on which wiring would be formed were removed by etching
(FIG. 12(c)). A 5000 .ANG. thick insulative layer 5 formed of amorphous
SiO.sub.2 was uniformly deposited thereon (FIG. 12(d)). Next, only
SiO.sub.2 on the amorphous thin film 3 was removed by etching to form a
groove in which wiring would be arranged (FIG. 12(e)). As a result, the
bottom surfaces of the grooves were made of the amorphous thin film 3. In
this embodiment, the width of the grooves, the width of the metal wiring,
was 0.8 .mu.m and the depth of the grooves was 4000 .ANG.. An ion beam
with low energy was irradiated on the above substrate 1 with the grooves
to remove an oxide film on the surface of the amorphous thin film 3.
Thereafter, Al was deposited by means of a thermal CVD method using TIBA
to obtain a metal wiring 4 (FIG. 12(f)). Selective growth that Al was
deposited only in the grooves could be performed at a substrate
temperature of 300.degree. C. or lower. Table 3 shows the Al deposition
speed in the grooves against substrate temperatures in the case where an
Al amorphous alloy, as the amorphous thin film 3, was formed on the groove
bottom surface. The Al amorphous alloys include Al.sub.30 Ta.sub.70,
Al.sub.40 Nb.sub.60, and Al.sub.50 V.sub.50. Further, in order to confirm
the selective growth, Table 3 also shows if selective growth for SiO.sub.2
was performed in parts other than the grooves. As comparative examples, a
film of amorphous SiO.sub.2, polycrystalline silicon or polycrystalline
silver was formed on the groove bottom surface. The Al deposition speeds
and selective growth of the comparative examples are shown in Table 3. As
compared with the Al amorphous alloys, if Al was deposited on the
amorphous SiO.sub.2 and polycrystalline silicon, sufficient Al deposition
speed could not be obtained at 300.degree. C. or lower and the surface
morphology of the filled Al was not satisfactory (rugged surface).
Moreover, as compared with the amorphous Al alloys, if Al was deposited on
polycrystalline silver, the deposition speed was slower and there were
parts where Al was not continuously filled in the line direction of
wiring.
Next, the crystalline properties of selectively filled Al were evaluated by
X-ray diffraction. The results are shown in Table 4. The Al orientation
was evaluated by measuring the FWHM of a rocking curve of an Al(111)
diffraction peak. Al filled in the grooves whose under-layer was formed of
the Al amorphous alloy has (111) high orientation with the FWHM of about
1.degree..
Al filled in the grooves whose bottom was formed of the Al amorphous alloy
was examined by a transmission electron microscope. The examination
revealed that a diameter of Al crystal grains was about 1 .mu.m to be
substantially the same as the wiring width and that these (111) crystal
grains were connected with small angle grain boundaries in the line
direction of the wiring. Further, there existed a region which consisted
of one crystal grain with length of 10 .mu.m or more in the wiring line
direction. This exhibits that a single-crystal Al wiring was partially
obtained which had more excellent stress-migration and electromigration
endurance than those of (111) high orientation.
Last, an accelerated test was conducted for studying the electromigration
endurance of the Al-filled wiring obtained in the embodiment. The results
are shown in FIG. 13. The test conditions are a substrate temperature of
150.degree. C. and a current density of 1.times.10.sup.7 A/cm.sup.2. Based
on the change in the rate of resistance change as time elapsed, the much
higher reliability than a conventional Al wiring was confirmed.
TABLE 3
__________________________________________________________________________
Al deposition speed (A/min)
Constituent material of
320
300 280
260
Selectivity
Continuity of
groove bottom surface
(.degree.C.)
(.degree.C.)
(.degree.C.)
(.degree.C.)
for SiO.sub.2
surface form
__________________________________________________________________________
Example 9-1
Al.sub.30 Ta.sub.70
1400
430 170
60 .circleincircle.
.circleincircle.
Example 9-2
Al.sub.40 Nb.sub.60
1400
430 170
60 .circleincircle.
.circleincircle.
Example 9-3
Al.sub.50 V.sub.50
1400
430 170
60 .circleincircle.
.circleincircle.
Comparative
Amorphous SiO.sub.2
110
30 10
0 x x
Example 9-1
Comparative
Polycrystalline Si
150
50 20
0 .DELTA.
x
Example 9-2
Comparative
Polycrystalline Ag
430
150 60
20 .largecircle.
.DELTA.
Example 9-3
__________________________________________________________________________
TABLE 3
______________________________________
Constituent material of
Al (111)
groove bottom surface
FWHM (.degree.)
______________________________________
Example 9-4 Al.sub.30 Ta.sub.70
1.0
Example 9-5 Al.sub.40 Nb.sub.60
1.1
Example 9-6 Al.sub.50 V.sub.50
1.0
______________________________________
EXAMPLE 10
Referring to FIG. 14, an embodiment will be described.
As shown in FIG. 14, a SiO.sub.2 insulative layer 5 was formed on a
semiconductor substrate 1 with a functional element 31 by means of a CVD
method. A region destined for a contact part was removed by etching to
from a contacting hole 32. In order to obtain the excellent contact
properties, a natural oxide film which was formed on the semiconductor
substrate 1 of the contacting hole bottom surface was removed by
hydrofluoric acid cleaning. In order to prevent re-oxidization, it was
rinsed with pure water with a low oxygen concentration and then dried by
highly pure nitrogen gas purge. An Al--Ta amorphous thin film 3 was formed
on the substrate by a multi-sputter apparatus. The sputtering conditions
are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Al--Ta mosaic target
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 0.20 Pa
Applied power: 10 W/cm.sup.2
Film thickness: 400 .ANG.
Composition analysis revealed that the formed film was Al.sub.55 Ta.sub.45.
X-ray diffraction revealed that the film was amorphous. Although the Al
amorphous thin film 3 was formed by a sputter method in this embodiment, a
similar amorphous film can be formed by a CVD method or vapor deposition
method. Further although a Al--Ta mosaic target was used in the sputtering
of the Al amorphous thin film 3, a similar amorphous thin film can be
obtained by the other methods such as simultaneous sputtering with an
Al/Ta binary target or alternate laminating Al and Ta in thin thicknesses.
Keeping vacuum, an Al film was formed thereon by a sputter method. The
sputtering conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Al target
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 1 Pa
Applied power: 5 W/cm.sup.2
Film thickness: 4000 .ANG.
The Al film thus formed was evaluated for the orientation and crystalline
properties by X-ray diffraction. The FWHM of a (111) rocking curve was
1.0.degree. and excellent orientation was observed. Namely satisfactory
orientation was obtained. Although the Al film was formed by a sputter
method in this embodiment, similarly satisfactory layers can be obtained
by means of a CVD method and vapor deposition method.
Thereafter a resist was formed in a given pattern by standard lithography
technique and dry etching of the Al film and Al--Ta amorphous thin film 3
was simultaneously conducted using an etching gas containing chlorine to
process the Al film into a metal wiring 2. After the processing, residue
was not observed by SEM (scanning electron microscope) examination and the
processability was excellent. This sample was subjected to thermal
treatment for 15 minutes at 450.degree. C. in a forming gas (N.sub.2
:H.sub.2 =9:1) and then a leak current and contact resistance in a
conjunction part were measured. They were not changed by the thermal
treatment and the excellent barrier property was confirmed.
EXAMPLE 11
Referring to FIG. 15, an embodiment will be described.
For examining the electromigration endurance of an Al wiring, an Al--Ta
amorphous thin film and Al film were formed on a silicon substrate with a
thermal oxide film under condition similar to Example 10. As shown in FIG.
15, by using this substrate, a test substrate 24 was made which had an
anode 21, a cathode 22 and a 0.8 .mu.m wide wiring part 23 connecting
these electrodes. The orientation and crystalline properties of an Al film
of this test substrate was evaluated by X-ray diffraction. As a result,
similarly to Example 10, the FWHM of a (111) rocking curve was
1.0.degree..
A current at a current density of 2.times.10.sup.6 A/cm.sup.2 was flown in
the test substrate 24 at a test temperature of 200.degree. C. to measure
its average failure time. The value was 1000 hours or more, thereby
exhibiting that the test substrate had the high electromigration
endurance.
EXAMPLE 12
In a manner similar to Example 10, Al--Mo amorphous thin film was formed on
a substrate with functional elements thereon. As a result of composition
analysis, it was found that the formed film was Al.sub.60 Mo.sub.40. X-ray
diffraction revealed that the film was amorphous. An Al film formed
thereon was evaluated for the orientation and crystalline properties by
X-ray diffraction. As a result, the FWHM of a (111) rocking curve was
1.1.degree.. Satisfactory orientation was observed.
Thereafter a resist was formed in a given pattern by standard lithography
technique, and dry etching of the Al film and Al--Mo amorphous thin film
was simultaneously conducted using an etching gas containing chlorine to
process the Al film into a metal wiring. After the processing, residue was
not observed by SEM examination and the processability was excellent. This
sample was subjected to thermal treatment for 15 minutes at 450.degree. C.
in a forming gas (N.sub.2 :H.sub.2 =9:1) and then a section of a
conjunction part were measured. No alloy spike was not observed and the
excellent barrier property was confirmed.
EXAMPLE 13
In a manner similar to Example 10, Al--Nb--Si amorphous thin film was
formed on a substrate with functional elements thereon. As a result of
composition analysis, it was found the formed film was Al.sub.40 Nb.sub.55
Si.sub.5. X-ray diffraction revealed that the film was amorphous. An Al
film formed thereon was evaluated for the orientation and crystalline
properties by X-ray diffraction. As a result, the FWHM of a (111) rocking
curve was 1.3.degree.. Excellent orientation was observed.
Thereafter a resist was formed in a given pattern by standard lithography
technique, and dry etching of the Al film and Al--Nb--Si amorphous thin
film was simultaneously conducted using an etching gas containing chlorine
to process the Al film into a metal wiring. After the processing, residue
was not observed by SEM examination and the processability was excellent.
This sample was subjected to thermal treatment for 15 minutes at
450.degree. C. in a forming gas (N.sub.2 :H.sub.2 =9:1) and then a section
of a conjunction part was measured. No alloy spike was observed and the
excellent barrier property was confirmed. Moreover, since Si was
contained, the thermal stability of the amorphous thin film was improved.
Even when the amorphous thin film was subjected to further higher thermal
treatment, any crystallization and reaction were not observed. In the
cases of Ge, P and B, this advantageous effects were also obtained.
EXAMPLE 14
Referring to FIG. 16, an embodiment will be described.
A six-inch silicon wafer with a 4000 .ANG. insulative film 5 formed of a
thermal oxide film was used as a substrate 1. A PtZr amorphous thin film 3
was formed by means of a multi-target sputter apparatus as shown in FIG.
5. The sputtering conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. PtZr mosaic target
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 0.20 Pa
Applied power: 10 W/cm.sup.2
Film thickness: 500 .ANG.
Composition analysis revealed that the formed film was Pt.sub.21 Zr.sub.79.
X-ray diffraction revealed that the film was amorphous.
Next, keeping vacuum, Pt was sputtered on the amorphous PtZr film. The
sputter conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Pt target
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 1 Pa
Applied power: 5 W/cm.sup.2
Film thickness: 1000 .ANG.
The Pt film 33 thus formed as an under electrode was evaluated for the
orientation and crystalline properties by X-ray diffraction. The (111)
orientation FWHM was 1.4.degree. and satisfactory crystalline properties
were observed.
Next, on this under electrode layer, a strontium titanate film 34 was
formed as a dielectric thin film by means of a RF magnetron sputter
method. A sintered body of strontium titanate was used as a target. The
sputter conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. SrTiO.sub.3 target
Substrate temperature: 500.degree. C.
Sputter gas: Ar/O.sub.2
Gas pressure: 1 Pa
Applied power: 5 W/cm.sup.2
Film thickness: 5000 .ANG.
The orientation and crystalline properties of the dielectric thin film were
evaluated by X-ray diffraction. The (111) orientation of Pt film 33 was
continued and the (111) orientation FWHM was 1.5.degree.. An Au film 35
was vapor deposited on this dielectric thin film as an upper electrode and
the capacitor property thereof was evaluated. It was found that dielectric
constant and leak current were satisfactory values. On the other hand, the
orientation FWHM of a Pt film directly formed on the thermal oxide film
was 9.2.degree.. When a strontium titanate film was formed thereon under
the above conditions, the orientation FWHM was 9.5.degree..
EXAMPLE 15
Like Example 14, using a six-inch silicon wafer substrate with a 4000 .ANG.
thermal oxide film, a Pt.sub.21 Zr.sub.79 film was formed as an amorphous
thin film by means of a multi-target sputter apparatus.
Next, keeping vacuum, a PtTi film was formed by sputtering as an under
electrode on the amorphous Pt.sub.21 Zr.sub.79 film. The sputter
conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Pt/Ti binary targets
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 1 Pa
Applied power: 5 W/cm.sup.2
Film thickness: 1000 .ANG.
The PtTi film thus formed was subjected to composition analysis. The
analysis revealed that the composition thereof was Pt.sub.88 Ti.sub.12.
The orientation and crystalline properties thereof were evaluated by X-ray
diffraction. The (111) orientation FWHM was 1.4.degree. and satisfactory
crystalline properties were observed.
Next, on this under electrode, a ferrodielectric thin film of lead titanate
zirconate was grown by means of a RF magnetron sputter method. A used
target was a sintered body where powder of lead titanate zirconate added
with lead oxide 10 mol % rich was sintered at 1200.degree. C. The
sputtering conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Pb(ZrTi)O.sub.3 target (PbO 10 mol % RICH)
Substrate temperature: 600.degree. C.
Sputter gas: Ar/O.sub.2
Gas pressure: 1 Pa
Applied power: 5 W/cm.sup.2
Film thickness: 5000 .ANG.
The orientation and crystalline properties of the obtained strong
dielectric thin film were evaluated by X-ray diffraction. The (111)
orientation of the PtTi film was continued and the (111) orientation FWHM
was 1.9.degree.. On the other hand, the orientation FWHM of a Pt film
directly formed on the thermal oxide film was 9.2.degree.. When a lead
titanate zirconate film was formed thereon under the above conditions, the
orientation FWHM was 9.8.degree..
EXAMPLE 16
Referring to FIG. 17, an embodiment will be described.
On a glass substrate 1', an AlTa amorphous thin film was formed as a
resistance heater film 12 by means of a multi-target sputter apparatus as
shown in FIG. 5. The sputter conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Al/Ta binary targets
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 0.20 Pa
Applied power: 10 W/cm.sup.2
As a result of composition analysis, it was found that the formed film was
Al.sub.25 Ta.sub.75. X-ray diffraction revealed that this film was
amorphous. In the same chamber, an Al thin film was sputtered thereon. The
sputter conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Al target
Substrate temperature: room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 1 Pa
Applied power: 5 W/cm.sup.2
The crystalline properties of the formed film were evaluated by X-ray
diffraction. This film was an oriented film with the FWHM 1.0.degree. of a
(111) rocking curve.
Next this Al film was processed by lithography and etching steps to form
electrodes 13, 13'. Further a SiO.sub.2 insulative film 14 was coated
thereon to prevent oxidation and improve abrasion resistance. A thermal
head thus formed was actually mounted in a printer and a recording test
was conducted. The test showed that fluctuation in record concentration
was smaller than a conventional thermal head even in a fine pattern. In
addition, an Al electrode was not degraded.
EXAMPLE 17
Referring to FIG. 18, an embodiment will be described.
On a glass substrate 1' with a height, an AlNa thin film was formed as a
resistance exothermic body film 12 by means of a multi-target sputter
apparatus as shown in FIG. 5. The sputter conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Al/Nb binary targets
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 0.20 Pa
Applied power: 10 W/cm.sup.2
As a result of composition analysis, it was found that the formed film was
Al.sub.40 Nb.sub.60. X-ray diffraction revealed that this film was
amorphous.
This Al--Nb film was processed by lithography and etching steps to remain
only on the height and vicinity thereof. Next this was placed in a chamber
again and subjected to Ar bias cleaning. Then an Al film was sputtered.
The sputter conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Al target
Substrate temperature: room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 1 Pa
Applied power: 5 W/cm.sup.2
The crystalline properties of the Al film formed on the flat part were
evaluated by X-ray diffraction. This film was an oriented film with the
FWHM of 1.2.degree. of a (111) rocking curve.
Next this Al film was processed by lithography and etching steps to form
electrodes 13, 13'. Further a SiO.sub.2 insulative film 14 was coated
thereon to prevent oxidation and improve abrasion resistance. The
recording test was conducted under the same conditions as Example 16. The
test showed the excellent properties.
EXAMPLE 18
Referring to FIG. 19, an embodiment will be described.
using a six-inch silicon wafer substrate 1 with a 4000 .ANG. insulative
oxide layer 5 of a thermal oxide film, an AlTa amorphous film 3 was formed
by means of a multi-target sputter apparatus as shown in FIG. 5. The
sputter conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Al/Ta binary targets
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 0.20 Pa
Applied power: 10 W/cm.sup.2
Film thickness: 1000 .ANG.
Composition analysis revealed that the formed film was Al.sub.45 Ta.sub.55.
X-ray diffraction revealed that the film was amorphous.
Next, in the surface of the AlTa amorphous thin film 3, grooves 38 were
formed by standard lithography and RIE steps. The depth of the grooves 38
was 100 .ANG. and the width thereof was 1000 .ANG..
After the AlTa amorphous thin film 3 with the grooves 38 was subjected to
Ar bias cleaning, an Al film was sputtered. The sputter conditions are
shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Al target
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 1 Pa
Applied power: 5 W/cm.sup.2
Film thickness: 4000 .ANG.
The Al film thus formed was evaluated for the orientation and crystalline
properties by X-ray diffraction. The (111) orientation FWHM was
1.2.degree. and satisfactory crystalline properties were observed.
Further, observation by a transmission electron microscope (TEM) revealed
that directions of Al <211> were substantially equal to the longitudinal
direction of the grooves 38 formed on the amorphous thin film 3 so that
the Al film 2 consisted of only small angle boundaries.
Next, this Al film was processed into a metal wiring for the EM test. Steps
for preparing a test sample were as follows: As shown in FIG. 15, a test
substrate 24 had an anode 21, a cathode 22 and a 0.8 .mu.m wide wiring
part 23 connecting these electrodes. The test substrate 24 was made by
standard lithography and RIE steps. A current at a current density of
2.times.10.sup.6 A/cm.sup.2 was flown to the wiring part 23 of the test
substrate 24 at a test temperature of 200.degree. C. It was confirmed that
even after the elapsed time of 1000 hours there was no failure. This
exhibits that since Al film was highly oriented and the Al film was a film
formed only of small angle grain boundaries, the electromigration
endurance was dramatically enhanced.
EXAMPLE 19
Referring to FIG. 20, an embodiment will be described.
Using a six-inch silicon wafer substrate 1 with a 4000 .ANG. insulative
layer 5 of a thermal oxide film, grooves were formed by means of standard
lithography and RIE steps.
A NiTa amorphous film 3 with grooves 30 was formed on the substrate 1 by
means of a multi-target sputter apparatus as shown in FIG. 5. The sputter
conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Ni/Ta binary targets
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 0.20 Pa
Applied power: 10 W/cm.sup.2
Film thickness: 100 .ANG.
Composition analysis revealed that the formed film was Ni.sub.50 Ta.sub.50.
X-ray diffraction revealed that the film was amorphous. A sectional
surface was examined by a SEM. The examination revealed that the grooves
30 were uniformly formed in the surface of NiTa amorphous film 3, the
depth of the grooves 30 being 1000 .ANG., the width thereof being 1000
.ANG..
After the NiTa amorphous thin film 3 was subjected to Ar bias cleaning, Al
was sputtered in a manner similar to Example 18. The formed Al film was
evaluated for the orientation and crystalline properties by X-ray
diffraction. The (111) orientation FWHM was 0.9.degree. and satisfactory
crystalline properties were observed.
Observation by a transmission electron microscope (TEM) revealed that
directions of Al (211) were substantially equal to the longitudinal
direction of the grooves formed on the amorphous thin film so that the Al
film consisted of only small angle grain boundaries.
EXAMPLE 20
Using a six-inch silicon wafer substrate with a 4000 .ANG. thermal oxide
film, an AlNb amorphous thin film was formed by means of a multi-target
sputter apparatus as shown in FIG. 5. The sputter conditions are shown
below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Al/Nb binary targets
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 0.20 Pa
Applied power: 10 W/cm.sup.2
Film thickness: 1000 .ANG.
Composition analysis revealed that the formed film was Al.sub.40 Nb.sub.60.
X-ray diffraction revealed that the film was amorphous.
In this AlNb amorphous thin film, grooves were formed by standard
lithography and RIE steps. The depth of the grooves was 100 .ANG. and the
width thereof was 1000 .ANG..
After the AlNb amorphous thin film with the grooves was subjected to Ar
bias cleaning, Al-0.1 at % Cu was sputtered as a metal thin film. The
sputter conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. AlCu alloy target
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 1 Pa
Applied power: 5 W/cm.sup.2
Film thickness: 4000 .ANG.
The AlCu film thus formed was evaluated for the orientation and crystalline
properties by X-ray diffraction. The (111) orientation FWHM was
0.9.degree. and satisfactory crystalline properties were observed. When
this film was subjected to thermal treatment at 450.degree. C. for 30
minutes, the orientation was further enhanced and the (111) orientation
FWHM become 0.7.degree..
Grain direction in a plane was examined by a transmission electron
microscope (TEM). It was found that since the grooves arranged in the
amorphous thin film controlled grain direction in a plane, the film was of
small angle grain boundaries. Further, a metal wiring was formed in a
manner similar to Example 18 for the EM test. Even after the elapse of
1000 hours there was no failure.
EXAMPLE 21
Referring to FIGS. 21 and 22, an embodiment will be described.
A 1000 .ANG. thick thermal oxide film was formed on a Si (100) six-inch
substrate 1 as an insulating layer 5. Thereafter, the following seven
samples were prepared. In a sample No. 1, the surface of amorphous
SiO.sub.2 (surface energy: 605 erg/cm.sup.2) was processed by lithography
and RIE steps to form grooves with a depth of 200 .ANG. (L/S=0.3/0.3
.mu.m) (FIG. 21(a)). Here, L/S is shown in FIG. 22. In a sample No. 2,
polycrystalline Ta (surface energy: 2150 erg/cm.sup.2) was sputtered on
the thermal oxide film to form a 500 .ANG. thick Ta film 39. Amorphous
SiO.sub.2 was sputtered to form a 200 .ANG. thick SiO.sub.2 film 43, and
the SiO.sub.2 film 43 was then processed to form grooves with a depth of
200 .ANG. (L/S=0.3/0.3 .mu.m) (FIG. 21(b)). In a sample No. 3,
polycrystalline Ta was sputtered on the thermal oxide film to form a 200
.ANG. thick Ta film 39. Subsequently, the Ta film 39 was processed to form
grooves with a depth of 200 .ANG. (L/S=0.3/0.3 .mu.m) (FIG. 21(c)). In a
sample No. 4, amorphous Ni.sub.62 --Nb.sub.38 (surface energy: 1326
erg/cm.sup.2) was sputtered on the thermal oxide film to form a 200 .ANG.
thick NiNb film 40. Subsequently, the NiNb film 40 was processed to form
grooves with a depth of 200 .ANG. (L/S=0.3/0.3 .mu.m) (FIG. 21(d)). In a
sample No. 5, amorphous Ta-60 at % Al (surface energy: 1640 erg/cm.sup.2)
was sputtered on the thermal oxide film to form a 200 .ANG. thick TaAl
film 41. Subsequently, the TaAl film 41 was processed to form grooves with
a depth of 200 .ANG. (L/S=0.3/0.3 .mu.m) (FIG. 21(e)). In a sample No. 6,
amorphous Ta-60 at % Al was sputtered on the thermal oxide film to form a
100 .ANG. thick TaAl film 41. Further amorphous SiO.sub.2 was sputtered to
form a 100 .ANG. thick SiO.sub.2 film 43. The SiO.sub.2 film 43 and TaAl
film 41 were processed to form grooves with a depth of 200 .ANG.
(L/S=0.3/0.3 .mu.m) (FIG. 21(f)). In a sample No. 7, a 200 .ANG. thick
polysrystalline Si (surface energy: 730 erg/cm.sup.2) film 42 was formed
on the thermal oxide film. Subsequently, the Si film 42 was processed to
form grooves with a depth of 200 .ANG. (L/S=0.3/0.3 .mu.m) (FIG. 21(g)).
The sections of the above samples are shown in FIG. 21. For the each
sample, pure Al was deposited on the above under layers at a substrate
temperature of 200.degree. C. in a thickness of 4000 .ANG. and then
processed into a four-terminal shape for the EM test. A wiring of a
measurement part had the width of 1 .mu.m and length of 2000 .mu.m. The EM
test was conducted at 150.degree. C. in 1.times.10.sup.7 A/cm.sup.2. The
results are shown in Table 5.
TABLE 5
______________________________________
No. 1 No. 2 No. 3 No. 4
No. 5 No. 6
No. 7
______________________________________
EM Test x x .largecircle.
.circleincircle.
.circleincircle.
.circleincircle.
x
______________________________________
.circleincircle.: no failure up to 1000 hours
.largecircle.: failed between 500 and 1000 hours
x: failure after 500 hours or less
EXAMPLE 22
A 1000 .ANG. thick thermal oxide film was formed on Si(100) six-inch
substrates and then a 200 .ANG. thick Ta-40 at % Al film was deposited by
sputtering. These samples were processed to form grooves of L/S as shown
in Table 6 by RIE. The resultant samples were subjected to Ar plasma
etching in a high vacuum sputter whose the degree of vacuum was on the
order of 10.sup.-10 Torr so that a surface oxide film of the Al--Ta film
surface was removed by Ar plasma etching. Subsequently, a pure Al film was
formed in a thickness of 4000 .ANG.. The EM test was conducted in a manner
similar to Example 21. The results are shown in Table 6.
TABLE 6
______________________________________
S (.mu.m)
L/S and EM test results
L 0.1 0.2 0.5 1.0
______________________________________
0.1 .circleincircle.
.circleincircle.
.smallcircle.
x
0.2 .circleincircle.
.circleincircle.
.smallcircle.
x
0.5 x .smallcircle.
x x
1.0 x .smallcircle.
x
______________________________________
.circleincircle.: no failure up to 1000 hours
.smallcircle.: failed between 500 and 1000 hours
x: failure after 500 hours or less
EXAMPLE 23
Referring to FIG. 23, an embodiment will be described.
using a six-inch silicon wafer substrate 1 with a 4000 .ANG. insulative
layer 5 of a thermal oxide film (FIG. 23(a)), grooves 36 were formed by
standard lithography and RIE steps (FIG. 23(b)). The depth of the grooves
36 was 100 .ANG. and the width thereof was 1500 .ANG..
A AlTa amorphous film 3 was formed on this substrate 1 by means of a
multi-target sputter apparatus as shown in FIG. 5 (FIG. 23(c)). The
sputter conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Al/Ta binary targets
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 0.20 Pa
Applied power: 10 W/cm.sup.2
Film thickness: 1000 .ANG.
Composition analysis revealed that the formed film was Al.sub.75 Ta.sub.25.
X-ray diffraction revealed that the film was amorphous. Subsequently, this
substrate 1 was subjected to thermal treatment at 450.degree. C. for 30
minutes so that the AlTa amorphous thin film 3 was crystallized to form an
intermetallic compound of Al.sub.3 Ta or a polycrystalline film 37 with
small angle grain boundaries in a grain diameter of 1 to 2 .mu.m (FIG.
23(d)). In the same chamber, an Al film was sputtered thereon (FIG.
23(e)). The sputter conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Al target
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 1 Pa
Applied power: 5 W/cm.sup.2
Film thickness: 4000 .ANG.
The Al film thus formed was evaluated for the orientation and crystalline
properties by X-ray diffraction. The (111) orientation FWHM was improved
to be 0.3.degree. and almost grain boundaries remaining in the Al film
were small angle boundaries.
Next, this Al thin film was processed into a metal wiring 2 for the EM
test. Steps for preparing a test sample were as follows: As shown in FIG.
15, a test substrate 24 had an anode 21, a cathode 22 and a 0.8 .mu.m wide
wiring part 23 connecting these electrode. The test substrate 24 was made
by standard lithography and RIE steps. A current at a current density of
2.times.10.sup.6 A/cm.sup.2 was loaded to the wiring part 23 of the test
substrate 24 at a test temperature of 200.degree. C. Even after the
elapsed time of 1000 hours there was no failure. This exhibits that since
the Al film was similar to single-crystal, the electromigration endurance
was dramatically enhanced.
EXAMPLE 24
Using a six-inch silicon wafer substrate with a 4000 .ANG. thermal oxide
film, grooves were formed by standard lithography and RIE steps. The depth
of the grooves was 500 .ANG. and the width thereof was 5000 .ANG.. The
space between the grooves was 3000 .ANG..
A AlNb amorphous film was formed on this substrate by means of a
multi-target sputter apparatus as shown in FIG. 5. The sputter conditions
are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Al/Nb binary targets
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 0.20 Pa
Applied power: 10 W/cm.sup.2
Film thickness: 400 .ANG.
Composition analysis revealed that the formed film was Al.sub.75 Nb.sub.25.
X-ray diffraction revealed that the film was amorphous. Subsequently, this
substrate was heated at 450.degree. C. for 30 minutes so that the AlNb
amorphous film was crystallized to form an intermetallic compound of
Al.sub.3 Nb. The intermetallic compound was filled in the grooves to be of
single-crystal. The surface of the resultant substrate was flatted by
polishing and then was placed into a chamber again. After Ar bias
cleaning, an Al-0.1 at % Cu alloy was sputtered as a metal thin film. The
sputter conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. AlCu alloy target
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 1 Pa
Applied power: 5 W/cm.sup.2
Film thickness: 4000 .ANG.
The AlCu film thus formed was processed into a metal wiring by a RIE step.
Moreover, in the EM test under the same conditions as those of Example 23,
even after the elapse of 1000 hours there was no failure.
EXAMPLE 25
Referring to FIG. 24, an embodiment will be described.
As shown in FIG. 24, on a Si wafer substrate 1 where a 1000 .ANG. thick
thermal oxide film was formed as an insulative layer 5, a 4000 .ANG. thick
pure Al thin film destined for a metal wiring 2 was formed by sputtering.
After the formation of this Al thin film, while keeping vacuum of
1.times.10.sup.-7 Torr, an Al--Ta amorphous thin film 3 was formed by
sputtering using an Al/Ta mosaic target. The thickness of the layer 3
varied 100, 300, and 500 .ANG.. At this time, after the formation of this
Al thin film, some samples were exposed to the air. The exposed samples
were then placed into a sputter apparatus again so that the Al--Ta
amorphous thin film 3 was formed on the pure Al thin film. Prior to
forming the amorphous thin film 3, a surface oxide of the exposed samples
was removed by RF--Ar plasma where the substrate 1 side was an electrode.
In the removal of the surface oxide, plasma etching was conducted until a
clear diffraction pattern of an Al thin film was observed by RHEED for the
surface of the Al thin film. The composition of the amorphous thin film 3
was Al.sub.20 Ta.sub.80.
The laminated structure of the metal film 2 of a pure Al and Al--Ta
amorphous thin film 3 was thus prepared. In order to examine occurrence
frequency of hillocks in the metal film, these thin samples were thermal
treated in a forming gas (N.sub.2 --H.sub.2) at 450.degree. C. for 30
minutes. Hillock density measured by an optical microscope and tracer type
device for measuring a film thickness (.alpha.-STEP) are shown in Table 7.
As shown in table 7, it was found that the existence of the amorphous thin
film 3 considerably reduced the number of hillocks and that even when the
thickness of the amorphous thin film 3 was 100 .ANG., this effect could be
obtained.
TABLE 7
______________________________________
Hillock density
Structure
Thickness of
after termal
of thin film
films (.ANG.)
treatment
______________________________________
Comparative
Al 4000 158/lmm
Example
Example a-AlTa//Al 500//4000 1/lmm
a-AlTa/Al 500/4000 3/lmm
a-AlTa//Al 300//4000 1/lmm
a-AlTa/Al 300/4000 4/lmm
a-AlTa//Al 100//4000 2/lmm
a-AlTa/Al 100/4000 5/lmm
______________________________________
// means that after a surface oxide was removed by Ar sputtering and the
removal was confirmed by RHEED, an amorphous thin film was formed. A
height peak of 500.ANG. or more by .alpha.-STEP was judged as a hillock
and the number of such hillocks was counted.
EXAMPLE 26
On a Si wafer substrate where a 1000 .ANG. thick thermal oxide film was
formed as an insulative layer, a 4000 .ANG. thick pure Cu thin film
destined for a metal wiring was formed by sputtering. After the formation
of this Cu thin film, while keeping vacuum of 1.times.10.sup.-7 Torr, a
Cu--Zr amorphous thin film or a Ni--Nb amorphous thin film was formed by
binary target sputtering. The thickness of the amorphous Cu--Zr alloy
layer or the amorphous Ni--Nb alloy layer varied 100, 300, and 500 .ANG..
At this time, after the formation of this Cu thin film, some samples were
exposed to the air. The exposed samples were then placed into a sputter
apparatus again so that the Cu--Zr amorphous thin film or the Ni--Nb
amorphous thin film was formed on the pure Cu thin film. Prior to forming
the amorphous thin film, a surface oxide of the exposed samples was
removed by RF--Ar plasma where the substrate side was an electrode. In the
removal of the surface oxide, plasma etching was conducted until a clear
diffraction pattern of a Cu thin film was observed by RHEED for the
surface of the Cu thin film. The composition of the amorphous thin film
was Cu.sub.50 Zr.sub.50 or Ni.sub.65 Nb.sub.35.
In order to examine the oxidization resistance of these thin films in the
laminated structure of the metal wiring of the pure Cu thin film, and
Cu--Zr or Ni--Nb amorphous thin film, these thin samples were subjected to
thermal treatment in the air at 500.degree. C. for 30 minutes. Here, Cu
and Ni are capable of a continuous series of solid solutions. The results
are shown in Table 8. As shown in Table 8, while in the pure Cu thin film
the surface become rugged due to volume expansion with increase in the
degree of oxidization, in the sample with the laminated Cu--Zr or Ni--Nb
amorphous thin film there was no significant difference in evaluation of
surface roughness by the use of a tracer type device for measuring a film
thickness (.alpha.-STEP) as shown in Table 8.
TABLE 8
______________________________________
Average roughness
Structure
Thickness of
after thermal
of thin film
films (.ANG.)
treatment (Ra, .ANG.)
______________________________________
Comparative
Cu 4000 790
Example
Example a-CuZr//Cu 500//4000 65
a-CuZr/Cu 500/4000 78
a-CuZr//Cu 300//4000 59
a-CuZr/Cu 300/4000 55
a-CuZr//Cu 100//4000 67
a-CuZr/Cu 100/4000 72
a-NiNb//Cu 500//4000 66
a-NiNb/Cu 500/4000 71
a-NiNb//Cu 300//4000 78
a-NiNb/Cu 300/4000 68
a-NiNb//Cu 100//4000 59
a-NiNb/Cu 100/4000 61
______________________________________
// means that after a surface oxide was removed by Ar sputtering and the
removal was confirmed by RHEED, amorphous thin film was formed.
EXAMPLE 27
Referring to FIG. 25, an embodiment will be described.
Using a six-inch silicon wafer substrate 1 with a 4000 .ANG. thick
insulative layer 5 formed of a thermal oxide film, Sn was vapor deposited
on the substrate to form a Sn film 51 in 1 mono layer (ML) (FIG. 25). A
K-cell (Knudsen-Cell) temperature was 1100.degree. C. and a substrate
temperature was 450.degree. C. Keeping vacuum, Al was vapor deposited on
the substrate 1 with the Sn film 51 to form a 1000 .ANG. thick Al film for
a metal wiring 2. A K-cell temperature was 1050.degree. C. and a substrate
temperature was room temperature.
The Al film thus formed was evaluated for the orientation by X-ray
diffraction. The (111) orientation FWHM was 2.0.degree. and satisfactory
crystalline properties were observed.
Besides Sn, in the cases of Ga, In, Cd, Bi, Pb and Tl, similar effects were
obtained.
EXAMPLE 28
Using a six-inch silicon wafer substrate with a 4000 .ANG. thick insulative
layer of a thermal oxide film, Pb was vapor deposited in 1 mono layer on
the substrate. A K-cell temperature was 600.degree. C. and a substrate
temperature was room temperature. Keeping vacuum, a 1000 .ANG. thick Cu
film was vapor deposited on the temperature with the Pb film. A K-cell
temperature was 1200.degree. C. and a substrate temperature was room
temperature.
The Cu film thus formed was evaluated for the orientation by X-ray
diffraction. The (111) orientation FWHM was 4.0.degree. and satisfactory
crystalline properties were observed.
In the cases of Tl, similar effects were obtained.
EXAMPLE 29
Using a six-inch silicon wafer substrate with a 4000 .ANG. thick insulative
layer of a thermal oxide film, an Al--Ta amorphous thin film was formed by
a multi-sputter apparatus. The sputter conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. AlTa alloy target
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 0.20 Pa
Film thickness: 400 .ANG.
Composition analysis revealed that the formed film was Al.sub.55 Ta.sub.45.
X-ray diffraction revealed that the film was amorphous.
Keeping vacuum, Sn was vapor deposited in one mono layer thereon. The vapor
deposition conditions were similar to Example 27. Further keeping vacuum,
a 1000 .ANG. thick Al film was vapor deposited on the substrate with the
Sn film. A K-cell temperature was 1050.degree. C. and a substrate
temperature was room temperature.
The Al film thus formed was evaluated for the orientation by X-ray
diffraction. The (111) orientation FWHM was 1.6.degree. and satisfactory
crystalline properties were observed.
EXAMPLE 30
Using a (111) oriented five-inch silicon wafer substrate, Bi was vapor
deposited in 0.5 and 1 mono layers (ML). A K-cell temperature was
600.degree. C. and a substrate temperature was room temperature. Keeping
vacuum, an Al film was vapor deposited on the substrates with the Bi films
in a thickness of 100 .ANG.. A K-cell temperature was 1050.degree. C. and
a substrate temperature was room temperature. For comparison, a sample
where an Al film was vapor deposited directly on the substrate was
prepared.
The Al films thus formed were evaluated for the orientation and crystalline
properties by RHEED and X-ray diffraction. The results are shown in FIG.
26. In the sample without Bi deposition, as shown in FIG. 26(a), a RHEED
pattern where (111) and (100) orientations were mixed was observed. On the
other hand, in the sample with Bi deposition in one atom layer, as shown
in FIG. 26(b), (100) orientation was not observed and satisfactory crystal
with the (111) orientation FWHM of 0.3.degree. was obtained. In the sample
with Bi deposition in 0.5 atom layer, although the (111) orientation FWHM
was 0.5.degree., (100) orientation was not observed.
The surface morphology of the Al films were examined by a SEM. In the
samples with Bi deposition, the high surface smoothness property was
confirmed.
The compositions of the Al films were analyzed by an AES. It was found that
Bi existed in the Al film surface, the Al film grain boundaries, and the
interface between the Al film and thermal oxide film.
Besides Bi, in the cases of Ga, In, Cd, Sn, Pb and Tl, similar effects were
obtained.
EXAMPLE 31
Using a six-inch silicon wafer substrate with a 4000 .ANG. insulative layer
of a thermal oxide film, Bi was vapor deposited in one mono layer. A
K-cell temperature was 600.degree. C. and a substrate temperature was room
temperature. Keeping vacuum, an Al film was vapor deposited on the
substrates with the Bi films in a thickness of 500 .ANG.. A K cell
temperature was 1050.degree. C. and a substrate temperature was room
temperature. For comparison, a sample where an Al film was vapor deposited
directly on the substrate was prepared.
The surface forms of the Al films were examined by a SEM. In the sample
with Bi deposition, crystal grain grew and the grain size become
1890.+-.20 .ANG.. On the contrary, in the sample without Bi deposition,
the grain diameter of crystal grain was 980.+-.20 .ANG..
The compositions of the Al films were analyzed by an AES. It was found that
Bi existed in the Al film surface, the Al film grain boundary, and the
interface between the Al film and thermal oxide film.
Besides Bi, in the cases of Ga, In, Cd, Sn, Pb and Tl, similar effects were
obtained.
EXAMPLE 32
A six-inch silicon wafer with a 4000 .ANG. insulative layer of a thermal
oxide film was used as a substrate. Bi was vapor deposited in one mono
layer on the substrate. The vapor deposition conditions were similar to
Example 31. Keeping vacuum, a 500 .ANG. thick Al film was vapor deposited
on the substrates with the Bi film. A K-cell temperature was 1050.degree.
C. and a substrate temperature was 400.degree. C. For comparison, a sample
where an Al film was vapor deposited directly on the substrate was
prepared.
The surface form of the Al film was examined by a SEM. In the sample with
Bi deposition, crystal grain grew and the average grain size become
3130.+-.20 .ANG.. On the contrary, in the sample without Bi deposition,
the grain diameter of crystal grain was 1230.+-.15 .ANG..
Besides Bi, in the cases of Ga, In, Cd, Sn, Pb and Tl, similar effects were
obtained.
EXAMPLE 33
A six-inch silicon wafer with a 4000 .ANG. insulative layer of a thermal
oxide film was used as a substrate. An Al--Ta amorphous thin film was
formed by means of a multi-target sputter apparatus. The sputter
conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Al--Ta mosaic target
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 0.20 Pa
Film thickness: 400 .ANG.
Composition analysis revealed that the formed film was Al.sub.55 Ta.sub.45.
X-ray diffraction revealed that the film was amorphous.
Keeping vacuum, Bi was vapor deposited in one mono layer thereon. The vapor
deposition conditions were similar to Example 31. Further, keeping vacuum,
Al was deposited on the substrate with the Bi film to form a 500 .ANG.
thick Al film. A K cell temperature was 1050.degree. C. and a substrate
temperature was room temperature. For comparison, a sample where an Al
film was vapor deposited directly on the substrate was prepared.
The Al film thus formed was examined by a SEM. In the sample with Bi
deposition, crystal grain grew and the grain diameter become 2970.+-.20
.ANG.. On the contrary, in the sample without Bi deposition, the grain
diameter of crystal grain was 960.+-.10 .ANG..
EXAMPLE 34
A high resistance Si (100) and Si (111) substrate were treated with 1% HF
and then washed with pure water in which the concentration of solved
oxygen was 10 ppb. Subsequently, a Cu or Al film was deposited on the Si
(100) substrate or Si (111) substrate respectively by a sputter apparatus
in which the degree of vacuum was 1.times.10.sup.-8 Torr or less. Ar
pressure during deposition was 1.times.10.sup.-3 Torr. Thereafter, the
resultant substrates were thermal treated under vacuum at 450.degree. C.
for 1 hour to process into a four-terminal wiring 1 .mu.m in width and 100
.mu.m in length. The kinds of grain boundaries were identified by
channelling pattern analysis of a SEM. It was found that 90% or more
thereof consisted of small angle boundaries with a relative misorientation
of 10.degree. or less, twin boundaries with the .SIGMA. value of 10 or
less and grain boundaries with a relative misorientation of 3.degree. or
less. Among these boundaries, only particular grain boundaries shown in
Table 9 were subjected to the EM test at 200.degree. C. and a current
density of 2.times.10.sup.6 A/cm.sup.2. Further, after the Cu and Al films
were processed into a pattern with a wiring width of 0.5 .mu.m and an
entire wiring length of 1 m, a 4000 .ANG. thick PSG film was formed by a
thermal CVD method and a 4500 .ANG. thick SiN film was formed by a plasma
CVD method. Thereafter, a stress-migration (SM) test was conducted by
keeping the test samples at 150.degree. C. for 1000 hours. The SM test
exhibited the excellent result that the defective percent was 0%.
TABLE 9
______________________________________
Relative
Result
Orientation mis- of EM
Wiring
direction .SIGMA. value
orientation
test
______________________________________
Cu (100) 5 36.9.degree.
.circleincircle.
13 22.6.degree.
.largecircle.
Al (111) 3 60.degree.
.circleincircle.
64.degree.
x dislocation of
4.degree. for
coincidence
boundary
63.degree.
.largecircle.
dislocation of
3.degree. for
coincidence
boundary
7 38.2.degree.
.circleincircle.
13 27.8.degree.
.largecircle.
19 48.8.degree.
x
______________________________________
.circleincircle. lifetime 1000 hours or more
.largecircle. lifetime 500-1000 hours
x lifetime 500 hours or less
EXAMPLE 35
On a high resistance (111) silicon wafer, a (111) orientated Al film was
formed in a thickness of 4000 .ANG. by high vacuum sputtering. Before Al
film deposition as shown in Table 10, the following six kinds of
pretreatment silicon wafer were conducted;
1. after 1% HF treatment, rinsing with ultra pure water with the dissolved
oxygen concentration of 5 ppb under an air-closed condition,
2. after 1% HF treatment, rinsing with ultra pure water with the dissolved
oxygen concentration of 5 ppb under a condition of open to the air,
3. after 1% HF treatment, rinsing with ultra pure water with the dissolved
oxygen concentration of 50 ppb under an air-closed condition,
4. after 1% HF treatment, rinsing with ultra pure water with the dissolved
oxygen concentration of 50 ppb under a condition of open to the air,
5. after 1% HF treatment, rinsing with ultra pure water with dissolved
oxygen concentration of 1 ppm under an air-closed condition, and
6. after 1% HF treatment, rinsing with ultra pure water with the dissolved
oxygen concentration of 1 ppm under a condition of open to the air.
Thereafter, they were processed to form a 0.5 .mu.m wide four-terminal
pattern where the length of a measurement part was 100 .mu.m. The
electromigration endurance was measured at 200.degree. C. and a current
density of 2.times.10.sup.6 A/cm.sup.2. Moreover, the SM test was also
conducted like Example 34.
The characteristics in contact parts were examined in the following manner.
A contact with a diameter of 0.5 .mu.m in which P was ion-plantated was
used. As pretreatment, choline treatment, diluted HF treatment, and the
above water-washing were successively conducted. An Al film was formed and
then processed into a Kelvin pattern. After thermal treatment at
450.degree. C. for 30 minutes in a forming gas (N.sub.2 :H.sub.2 =8:2),
the contact resistance was measured.
Regarding the wiring processability, a shape after wiring processing was
observed by a SEM. A thin piece was made from a wiring sample and the
piece was subjected to selected-area diffraction by an electron microscope
to examine the relative misorientation of adjacent grains. These results
are shown in Table 10.
Further, for the Al film sample processed with pretreatment 1, Al film
orientation was identified by a X-ray diffraction method, and the sample
was processed such that the wiring line direction was in parallel with a
{111} plane. The sample subjected to the above SM test was observed by a
SEM. It was found that voids formed in a trapezoidal shape substantially
in parallel with a wiring line direction. No failure was observed.
TABLE 10
__________________________________________________________________________
% of relative
misorientation
Process-
EM SM Contact
Kind of water rinse
10.degree. or less
ability
failure time
defective (%)
defective (%)
__________________________________________________________________________
02 5 ppb, air closed
100% .largecircle..largecircle..largecircle.
1000 hrs. or more
0% 0%
open to air
80% .largecircle..largecircle.
200 hrs.
1% 0.1%
02 50 ppb, air closed
97% .largecircle..largecircle..largecircle.
1000 hrs. or more
0% 0%
open to air
72% .largecircle..largecircle.
160 hrs.
2% 0.6%
02 1 ppm, air closed
90% .largecircle..largecircle..largecircle.
1000 hrs. or more
0.1% 0%
open to air
10% .largecircle.
10 hrs.
5% 3%
__________________________________________________________________________
EXAMPLE 36
A Cu film was deposited on a MgO (100) substrate in a thickness of 4000
.ANG. by super high vacuum sputtering to form a Cu film. An electron
microscope observation revealed that this Cu film was a {100} epitaxial
film containing twin boundaries. This Cu film was processed into a
four-terminal pattern 0.5 .mu.m in width and 1 mm in length to form a
metal wiring. The EM test was conducted. The test conditions were a wiring
temperature of 300.degree. C. and a current density of 2.times.10.sup.6
A/cm.sup.2. Although twin was observed in a wiring, there was no failure
after a welding test of 1000 hours.
EXAMPLE 37
A (111) oriented Al film was formed in a thickness of 4000 .ANG. on a high
resistance (111) silicon wafer substrate by high vacuum sputtering. At
this time, as a pretreatment, the substrate was treated with 1% HF, and
washed with ultra pure water in which the dissolved oxygen concentration
was 5 ppb under air-closed condition. Thereafter a 0.5 .mu.m wide
four-terminal pattern, where the length of a measurement part was 1000
.mu.m, was prepared to form a metal wiring. After electrical current
loading at 150.degree. C. of five current densities shown in Table 11,
thermal treatment was conducted in a forming gas (N.sub.2 :H.sub.2 =8:2)
at 400.degree. C. for 30 minutes. Then the resultant substrate was checked
for occurrence of pits (Si spike) in the wiring. Moreover, a wiring
pattern with L/S of 1 .mu.m/1 .mu.m was prepared and subjected to similar
processes. Then, the Al (111) orientation FWHM was examined by X-ray. The
results are also shown in Table 11.
TABLE 11
______________________________________
Current 0 1.0 .times.
5 .times. 10.sup.6
1 .times. 10.sup.7
2 .times. 10.sup.7
3 .times. 10.sup.7
density(A/cm2) 10.sup.6
Amount of pits
many several none none none many
(after thermal (grown by
treatment) current
loading)
FWHM 0.3.degree.
0.2.degree.
0.15.degree.
0.15.degree.
0.15.degree.
0.15.degree.
______________________________________
EXAMPLE 38
Referring to FIG. 27, an embodiment will be described.
A 1000 .ANG. SiO.sub.2 thick thermal oxide film was formed on a Si (100)
substrate 1 as an insulative layer 5 and thereafter a 300 .ANG. thick
amorphous Al.sub.30 Ta.sub.70 film 52 was formed by dual simultaneous
sputtering. After forming the films, grooves 54 with L/S of 1500
.ANG./1500 .ANG. and depth of 300 .ANG. were formed by lithography.
Moreover, after evacuating upto 1.times.10.sup.-8 Torr or less the
resultant substrate was exposed to plasma by bias cleaning where a bias
voltage of -50V was applied to the substrate for 5 minutes, thereby
removing an oxide film on the Ta--Al film 52. Subsequently, an Al film was
formed in a thickness of 4000 .ANG.. For comparison, a sample was prepared
by that a 4000 .ANG. thick Al film was formed directly on SiO.sub.2. The
Al films of these samples were processed into a 0.5 .mu.m wide
four-terminal metal wiring pattern where the length of a measurement part
was 1000 .mu.m. After electrical current loading at 200.degree. C. of a
density of 1.times.10.sup.7 A/cm.sup.2 for a period of time as shown in
Table 12, thermal treatment was conducted in a forming gas (N.sub.2
:H.sub.2 =8:2) at 400.degree. C. for 30 minutes. Then the resultant
samples were checked for occurrence of hillocks in the wiring. The results
are shown in Table 12.
Each of these samples were processed into the wiring pattern with L/S of 1
.mu.m/1 .mu.m. Similar processes were conducted. Then the Al (111)
orientation FWHM was measured by X-ray. The results are also shown in
Table 12.
TABLE 12
______________________________________
On SiO.sub.2
On surface processed Ta--Al
______________________________________
Current loading
Failure 30 secs.
1 min. 10 mins.
time during loading
Amount of hillocks
-- many None None
FWHM 8.degree. 0.3.degree.
0.2.degree.
0.2.degree.
______________________________________
EXAMPLE 39
An 4000 .ANG. thick Al film was formed on a high resistance (111) silicon
wafer substrate by high vacuum sputtering and thermal CVD methods. At this
time, as a pretreatment, the substrate was treated with 1% HF, rinsed with
ultra pure water where the dissolved oxygen concentration was 5 ppb under
air-closed condition, and then dried at N.sub.2 atmosphere where the vapor
concentration was 10 ppb or less. In the high vacuum sputter method, the
vacuum degree was 1.times.10.sup.-9 Torr, a dew point of Ar was
-90.degree. or less, and an Ar pressure was 1.times.10.sup.-3 Torr at the
time of forming. In the thermal CVD method, TIBA was used as a gas source.
The formed Al film was observed by a TEM. As a result, the sputtered Al
film contained small angle grain boundaries formed in dislocation arrays.
X-ray diffraction revealed that the sputtered Al film was of
single-crystal with the (111) orientation FWHM of 0.3.degree.. On the
other hand, the CVD film was of single-crystal containing no small angle
grain boundaries, and had the (111) orientation FWHM of 0.17.degree. by
X-ray diffraction.
The above film was processed into a four-terminal pattern where the width
of wiring part was 0.5 .mu.m and the length thereof was 100 .mu.m, thereby
forming a metal wiring and pad part. The pad consisted of aggregation of
fine lines in a shape of FIG. 4. The width of the fine line was 0.5 .mu.m,
the spacing between the fine lines was 0.5 .mu.m, and the spacing between
branch points was 0.5 .mu.m. In such pattern, the electronmigration
endurance was examined by a in situ SEM observation at a current density
of 2.times.10.sup.7 A/cm.sup.2 at 200.degree. C. As a result, in the both
films, voids moved inside the wiring, passed branch points one after
another in the pad part, and then reached a fine line in the outer most
periphery of the pad part. Thus, fine lines in the center of pad part were
sound. Neither of increase in electric resistance nor failure was
observed.
Further, after the wiring processing, a 4000 .ANG. thick SiO.sub.2 film was
formed on the wiring by a thermal CVD method and a 7500 .ANG. thick SiN
film was formed by a plasma CVD method. This was subjected to an identical
electromigration test. Stress-migration (SM) induced voids were similarly
accumulated in a fine line in the mostly outer periphery of the pad part.
Neither of increase in electric resistance nor failure was observed in the
centor of the pad part.
EXAMPLE 40
A Cu film was deposited in a thickness of 4000 .ANG. on a MgO (100)
substrate by super high vacuum sputtering. An electron microscope
observation revealed, that this film was a {100} epitaxial film containing
twin boundaries.
The above film was processed into a four-terminal pattern where the width
of a wiring part was 1.0 .mu.m and the length thereof was 100 .mu.m,
thereby forming a metal wiring and pad part. The pad part consisted of
aggregation of fine lines in a shape of FIG. 4. The width of the fine line
was 1.0 .mu.m, the spacing between the fine lines was 1.0 .mu.m, and the
spacing between branch points was 1.0 .mu.m. In such pattern, the
electronmigration endurance was examined by a in situ SEM observation at a
current density of 2.times.10.sup.7 A/cm.sup.2 at 250.degree. C. As a
result, voids moved inside the wiring, passed branch points one after
another in the pad part, and then reached a fine line of outer most
periphery of the pad part. Fine lines in the centor of the pad part were
sound. Neither of increase in electric resistance nor failure was observed
inside the pad part.
EXAMPLE 41
A 1000 .ANG. thick thermal oxide film was formed on a (100) Si substrate as
an insulative layer, and a TiN film was then formed to be subjected to
600.degree. C. thermal treatment in a N.sub.2 atmosphere. Various bias
voltages as shown in Table 13 were applied to the resultant substrate in
plasma, Ar: N.sub.2 =1:1, of 1.times.10.sup.-3 Torr. The TiN film was
subjected to sputter-etching. Thereafter a 4000 .ANG. thick Al film was
deposited by sputtering. The Al film was processed into a four-terminal
pattern 0.5 .mu.m in width and 1 mm in length, thereby forming a metal
wiring. The EM test was conducted. The test conditions were a wiring
temperature of 200.degree. C. and a current density of 2.times.10.sup.6
A/cm.sup.2. The results are shown in Table 13. For comparison, there were
two type samples. One sample was prepared without sputter-etching of the
TiN film. Another sample was prepared with exposure to N.sub.2 plasma
after sputter-etching. These results are shown in Table 13.
TABLE 13
______________________________________
Etching bias voltage
EM endurance
______________________________________
Plasma etching - 50 V .circleincircle.
-100 V .smallcircle.
-120 V x
plasma etching +
- 50 V .circleincircle.
N2 plasma processing
Without etching
-- x
______________________________________
.circleincircle.: no failure up to 500 hours
.smallcircle.: failed between 300 and 500 hours
x: faulure after 300 hours or less
EXAMPLE 42
After a 1000 .ANG. SiO.sub.2 thermal oxide film was formed on a Si (100)
six-inch substrate as an insulative layer, amorphous thin films of
compositions as shown in Table 14 were formed by sputtering with the use
of a mosaic target or by simultaneous sputtering with the use of a multi
target. Subsequently, a 4000 .ANG. thick Cu film was formed. Since the
various amorphous thin films destined for an underlying layer were exposed
to the air, the surface of the amorphous thin films was cleaned by
sputter-etching prior to forming the Cu film for the purpose of removing
an oxide film on the surface. The conditions of this surface cleaning were
an Ar gas pressure of 1.0.times.10.sup.3 Torr, a 100 MHz RF power output
of 100 W, a substrate bias voltage of -50V and cleaning time of 4 minutes.
The crystalline properties of the underlying layer was confirmed by RHEED.
It was confirmed that the underlying layer was an amorphous thin film.
After the surface cleaning, the Cu film was formed under the following
conditions:
degree of vacuum: less than 1.times.10.sup.-8 Torr
Ar gas pressure: 1.0.times.10.sup.-3 Torr
100 MHZ RF power output: 400 W
cathode bias voltage: -300V
film forming speed: 40 .ANG./second.
The crystalline properties of the formed Cu film were evaluated by X-ray.
For evaluation of the EM endurance, this was processed into a
four-terminal pattern with a wiring width of 1 .mu.m and wiring length of
300 .mu.m, thereby forming a metal wiring. The electromigration test was
then conducted at a current density of 2.times.10.sup.6 A/cm.sup.2 at a
wiring temperature of 300.degree. C. These results are also shown in Table
14.
As a comparative example, a Cu film was formed directly on a SiO.sub.2
thermal oxide film. The comparative example was similarly evaluated. The
results are also shown in Table 14.
If an underlying layer may have composition slightly different from those
of Table 14 as far as the underlying material was amorphous, similar
results can be obtained. Further, a little amount of an additive may be
added to improve the corrosion resistance, processability and barrier
property.
If after forming an amorphous thin film, a Cu film was subsequently formed
while keeping vacuum of 1.times.10.sup.-8 Torr or less, surface cleaning
is not necessary.
TABLE 14
______________________________________
Underlying
material Cu (111) Intensity ratio
composition orienta- of Cu x-ray
EM
(at %) RHEED tion FWHM I (200)/I (111)
endurance
______________________________________
Cu.sub.75 Zr.sub.25
a 1.5 -- .circleincircle.
Cu.sub.50 Zr.sub.50
a 1.5 -- .circleincircle.
Cu.sub.60 Zr.sub.40
a 1.8 -- .circleincircle.
Cu.sub.30 Zr.sub.70
a 1.7 -- .circleincircle.
Ni.sub.35 Ta.sub.65
a 1.7 -- .circleincircle.
W.sub.70 Zr.sub.30
a 1.2 -- .circleincircle.
Ta.sub.50 Zr.sub.50
a 1.4 -- .circleincircle.
Mo.sub.70 Zr.sub.30
a 1.3 -- .circleincircle.
SiO.sub.2
a 10.1 0.039 x
______________________________________
a: amorphous
.circleincircle.: even after the elapsed time of 1000 hours, no failure
takes place
x: within 100 hours, a failure takes place
EXAMPLE 43
Referring to FIG. 28, an embodiment will be described.
100 .ANG. thick alloy thin films 56 of TiNb, TiTa, ZrNb, ZrTa, TiW, ZrMo,
TiY and ZrY were formed on Si substrates 1 with a 1000 .ANG. thick
insulative layer 5 of a thermal oxide film by multi-target sputtering
system using an Ar gas. An electric power applied to each target was
adjusted such that the compositions of the alloy thin films 56 were
Ti.sub.50 Nb.sub.50, Ti.sub.50 Ta.sub.50, Zr.sub.50 Nb.sub.50, Zr.sub.50
Ta.sub.50, Ti.sub.50 W.sub.50, Zr.sub.50 Mo.sub.50, Ti.sub.50 Y.sub.50,
and Zr.sub.50 Y.sub.50. Subsequently, keeping vacuum, the gas was replaced
with a N.sub.2 gas and the surface of the alloy thin film 56 was exposed
to N.sub.2 plasma by RF discharge where a substrate 1 was an electrode.
Then the crystalline properties of the metal thin film 56 was evaluated by
RHEED. It was found that an amorphous layer was formed at least on the
surface. Auger electron spectroscopy (AES) analysis revealed that the
amorphous layer contained the nitrogen. Thus it was supposed that the
amorphous layer consisted of amorphous nitride. For comparison, a sample
which was not N.sub.2 plasma processed was prepared. These alloy thin
films thus formed were exposed to the air, and thereafter a 4000 .ANG.
thick metal film 2 of a pure Al or pure Cu thin films was deposited on the
alloy thin films 56. Prior to forming the metal film 2, some thereof were
subjected to etching of the alloy thin film 56 surface of an underlying
layer by Ar plasma. Next, the crystalline properties of the obtained pure
Al or pure Cu thin film were evaluated with the FWHM of Al and Cu (111)
rocking curve by X-ray diffraction using a CuK.alpha. line. The results
are shown in Table 15. As a result, even if the alloy thin films 56
subjected to N.sub.2 plasma process were exposed to the air, an Al or Cu
thin film 2 with the high (111) crystalline orientation could be formed on
the alloy thin films 56 without Ar plasma etching of the surface,
TABLE 15
______________________________________
Alloy N2 plasma
Ar surface (111) orientation FWHM
thin film
process etching Al Cu
______________________________________
TiNb .smallcircle.
.smallcircle.
0.8 1.53
.smallcircle.
x 0.85 1.57
x .smallcircle.
0.75 1.46
x x 6.3 8.2
TiTa .smallcircle.
.smallcircle.
0.8 1.55
.smallcircle.
x 0.75 1.53
x .smallcircle.
0.75 1.48
x x 5.9 7.5
ZrNb .smallcircle.
.smallcircle.
0.56 1.32
.smallcircle.
x 0.61 1.33
x .smallcircle.
0.52 1.27
x x 6.7 8.4
ZrTa .smallcircle.
.smallcircle.
0.66 1.44
.smallcircle.
x 0.68 1.53
x .smallcircle.
0.72 1.37
x x 6.82 8.1
TiW .smallcircle.
.smallcircle.
0.72 1.54
.smallcircle.
x 0.75 1.43
x .smallcircle.
0.93 1.72
x x 6.91 9.65
ZrMo .smallcircle.
.smallcircle.
0.81 1.73
.smallcircle.
x 0.79 1.67
x .smallcircle.
0.89 1.88
x x 5.69 8.71
TiY .smallcircle.
.smallcircle.
0.77 1.42
.smallcircle.
x 0.75 1.39
x .smallcircle.
0.81 1.45
x x 4.29 7.21
ZrY .smallcircle.
.smallcircle.
0.63 1.12
.smallcircle.
x 0.70 1.08
x .smallcircle.
0.71 1.05
x x 4.60 6.81
______________________________________
.smallcircle.: conducted
x: nonconducted
EXAMPLE 44
100 .ANG. thick thin films of carbide alloys as shown in Table 16 were
formed on a Si substrate 1 with a 1000 .ANG. thick insulative layer of a
thermal oxide film by multi-target sputtering system using metal targets
and a carbon target. An electric power applied to each target was adjusted
such that the compositions of the carbide alloy thin films become those as
shown in Table 16. Then the crystalline properties of the thin film
surface was evaluated by RHEED to obtain halo pattern suggesting that this
was amorphous. The carbide alloy thin film thus obtained were exposed to
the air, and thereafter a 4000 .ANG. thick metal wiring of a pure Al or
pure Cu thin films was formed on these carbide alloy thin films. Prior to
forming the metal films, some thereof were subjected to etching of the
carbide alloy thin film surface of an underlying layer by Ar plasma. The
crystalline properties of the pure Al or pure Cu thin film were evaluated
with the FWHM of Al and Cu (111) rocking curve by X-ray diffraction using
a CuK.alpha. line. The results are shown in Table 16. As a result, even if
the carbide alloy thin films were exposed to the air and the surface
thereof was not previously subjected to Ar plasma etching, the Al or Cu
thin film with the high (111) crystalline orientation could be formed on
the carbide alloy thin films.
TABLE 16
______________________________________
Carbide alloy
Ar surface (111) orientation FWHM
thin film etching Al Cu
______________________________________
TiNbC2 .smallcircle.
0.9 1.45
x 0.92 1.62
TiTaC2 .smallcircle.
0.58 1.23
x 0.55 1.21
ZrNbC2 .smallcircle.
0.54 1.22
x 0.63 1.33
ZrTaC2 .smallcircle.
0.78 1.41
x 0.82 1.55
TiWC2 .smallcircle.
0.73 1.43
x 0.74 1.35
ZrMoC2 .smallcircle.
0.82 1.73
x 0.77 1.67
______________________________________
.smallcircle.: conducted
x: nonconducted
EXAMPLE 45
A six-inch silicon wafer with a 1000 .ANG. thermal oxide film was used as a
substrate and Bi was vapor deposited on the substrate. The vapor
deposition conditions were similar to those of Example 31. Keeping vacuum,
Al was vapor deposited in a thickness of 200 .ANG. to 1000 .ANG. on the
substrate deposited with Bi. A K-cell temperature was 1200.degree. C. and
a substrate temperature was room temperature. After the film formation,
the substrate temperature was raised to 400.degree. C. and subjected to
thermal treatment for 3 hours.
The surface morphology and grain size of the Al film was examined by a SEM
and TEM. As a result, a grain size of an Al film with Bi was 7810.+-.30
.ANG., while a grain size of an Al film without Bi was 1680.+-.20 .ANG..
Namely, it was confirmed that a grain size of an Al film with Bi was
larger than that of an Al film without Bi.
In the case of Ga, In, Cd, Sn, Pb or Tl, similar results were obtained.
EXAMPLE 46
A six-inch silicon wafer with a 1000 .ANG. thermal oxide film was used as a
substrate. Al was deposited on the substrate in thicknesses of 200 .ANG.
to 1000 .ANG., and 1 ML of Bi was deposited simultaneously at beginning of
the Al deposition while rotating the substrate. The Bi deposition
conditions were similar to those of Example 31. The Al deposition
conditions were that a K-cell temperature was 1200.degree. C. and a
substrate temperature was room temperature.
The surface morphology and grain size of the Al film was examined by a SEM
and TEM. As a result, a grain size of an Al film with Bi was 4370.+-.20
.ANG., while a grain size of an Al film without Bi was 1170.+-.15 .ANG..
Namely, it was confirmed that a grain size of an Al film with Bi was
larger than that of an Al film without Bi. SEM photographs of these
samples are shown in FIGS. 29(a) and (b). FIG. 29(a) shows a SEM
photograph of the surface of the sample where a 500 .ANG. Al film was
formed on SiO.sub.2. FIG. 29(b) shows a SEM photograph of the surface of
the sample where a 500 .ANG. Al film with 1 ML Bi formed on SiO.sub.2.
Even if Bi was deposited at the middle time of the Al deposition or before
the end thereof, the similar effects could be obtained.
In the case of Ga, In, Cd, Sn, Pb or Tl, similar results were obtained.
EXAMPLE 47
A six-inch silicon wafer with a 1000 .ANG. thermal oxide film was used as a
substrate. A film of Al crystal grains with (111) orientation against the
substrate was formed on the substrate by a thermal CVD apparatus. The film
forming conditions are shown below.
Source gas: Triisobuthyl aluminum
Method for supplying the source gas: Bubbling system by Ar
Substrate temperature: 400.degree. C.
Ar gas flow amount: 20 sccm
The density of Al crystal grains forming the film under these conditions
was 5.times.10.sup.7 to 1.times.10.sup.8 /cm.sup.2.
Bi was vapor deposited on the substrate under conditions similar to those
of Example 31. Keeping vacuum, Al was vapor deposited in a thickness of
200 .ANG. to 1000 .ANG. on the substrate deposited with Bi. A K-cell
temperature was 1200.degree. C. and a substrate temperature was room
temperature.
The surface morphology of the Al film was observed by a SEM and TEM. As a
result, a grain size of an Al film with Bi was 3610.+-.15 .ANG., while a
grain size of an Al film without Bi was 1140.+-.20 .ANG.. Namely, it was
confirmed that a grain size of an Al film with Bi was larger than that of
an Al film without Bi.
Moreover, the Al film thus formed was evaluated for the orientation by
X-ray diffraction. The (111) orientation FWHM was 1.0.degree.. On the
other hand, the (111) FWHM of the Al film without pre-deposition of the Al
small crystal grains by CVD method was 2.0.degree.. Therefore, the
existence of (111) oriented Al small grains improves the final continuous
Al film (111) orientation.
In the case of Ga, In, Cd, Sn, Pb or Tl, similar results were obtained.
EXAMPLE 48
Grooves as shown in FIG. 30(a) were formed on a six-inch silicon wafer with
a 4000 .ANG. thermal oxide film. Al was vapor deposited on the substrate
in a thickness of 200 .ANG.. For Al deposition, a K-cell temperature was
1200.degree. C. and a substrate temperature was room temperature. The Al
morphology was observed by a SEM. As shown in FIG. 30(b), it was found
that Al 20 was uniformly deposited on both the grooves and SiO.sub.2
surface other than the grooves.
Further, Al was vapor deposited to form a 200 .ANG. thick Al film on a
similar substrate with grooves under the above conditions. A substrate
temperature was room temperature. Subsequently, keeping vacuum, thermal
treatment at 400.degree. C. for 3 hours was conducted. As shown in FIG.
(c), it was found that the grooves of the substrate were substantially
completely filled with a metal wiring 2 made of Al, and Al 20 hardly
remained on the SiO.sub.2 surface other than the grooves.
Next, Al was deposited on a similar substrate with grooves in thicknesses
of 200 .ANG. and 1 ML of Bi was simultaneously deposited at beginning of
the Al deposition. The Bi vapor deposition conditions were similar to
those of Example 31. The Al deposition conditions were the same as those
mentioned above. A substrate temperature was room temperature. As shown in
FIG. 30(d), it was found that the grooves of the substrate were
substantially completely filled with a metal wiring 2 made of Al, and Al
20 hardly remained on the SiO.sub.2 surface other than the grooves.
Namely, although the observation was conducted immediately after the film
formation at room temperature, the existence of Bi permitted to obtain
similar effects of the thermal treatment.
In the case of Ga, In, Cd, Sn, Pb or Tl, similar results were obtained.
EXAMPLE 49
A six-inch silicon wafer with a 4000 .ANG. thermal oxide film was used as a
substrate. An AlTa film was formed by means of a multi-target sputter
apparatus as shown in FIG. 5. The sputter conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Al/Ta binary targets
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 0.20 Pa
Applied power: 10 W/cm.sup.2
Film thickness: 50 .ANG.
Composition analysis revealed that the formed film was Al.sub.25 Ta.sub.75.
X-ray diffraction revealed that the film was amorphous.
Next, Al was sputtered on the amorphous AlTa thin film as a conductive thin
film. The sputter conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Al target
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 1 Pa
Applied power: 5 W/cm.sup.2
Film thickness: 4000 .ANG.
The Al film thus formed was evaluated for the orientation by X-ray
diffraction. It was found that the Al film was a (111) orientated film
where the FWHM of an Al (111) peak rocking curve was 1.0.degree.. When
this thin film was subjected to thermal treatment at 300.degree. C. for 15
minutes, the FWHM was improved to be 0.8.degree.. Further when this thin
film was subjected to thermal treatment at 500.degree. C. for 15 minutes,
the amorphous underlying layer reacted with the conductive thin film to
form Al.sub.3 Ta phase and the amorphous thin film layer disappeared.
However, it was found that the specific resistance was unchanged and
orientation of the conductive thin film were further improved to be
0.6.degree., and the highly orientated film was formed on the thermal
oxide film.
Next, this conductive thin film was processed into a wiring for the EM
test. Steps for preparing a test sample were as follows: As shown in FIG.
15, a test substrate 24 had an anode 21, a cathode 22 and a 0.8 .mu.m wide
wiring part 23 connecting these electrode. The test substrate 24 was made
by standard lithography and RIE steps. An electrical current of
2.times.10.sup.6 A/cm.sup.2 was loaded to the wiring part 23 of the test
substrate 24 at a test temperature of 200.degree. C. It was confirmed that
even after the elapsed time of 1000 hours there was no failure. This
exhibits that since (111) orientation of the Al thin film which was the
conductive thin film was improved, the electromigration endurance was
dramatically enhanced.
EXAMPLE 50
A six-inch silicon wafer with a 4000 .ANG. thermal oxide film was used as a
substrate. An AlNb film was formed by means of a multi-target sputter
apparatus similar to Example 48. The sputter conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Al/Nb binary targets
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 0.20 Pa
Applied power: 10 W/cm.sup.2
Film thickness: 500 .ANG.
Composition analysis revealed that the formed film was Al.sub.75 Nb.sub.25.
X-ray diffraction revealed that the film was amorphous. Al was sputtered
on the amorphous Al.sub.75 Nb.sub.25 thin film as a conductive thin film
in similar manner to Example 49. The Al film thus formed was evaluated for
the orientation by X-ray diffraction. It was found that the Al film was a
(111) orientated film where the FWHM of a rocking curve was 1.5.degree..
Further, this thin film was subjected to thermal treatment at 400.degree.
C. for 15 minutes. As a result, the amorphous thin film layer was
crystallized and the amorphous thin film layer disappeared. At the same
time the FWHM was improved to be 0.9.degree.. The EM test was conducted
under the same conditions as those of Example 49. Even after the elapsed
time of 1000 hours there was no failure.
EXAMPLE 51
A six-inch silicon wafer with a 4000 .ANG. thermal oxide film was used as a
substrate. A CuTi film was formed by means of a multi-target sputter
apparatus similar to Example 49. The sputter conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Cu/Ti binary targets
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 0.20 Pa
Applied power: 10 W/cm.sup.2
Film thickness: 500 .ANG.
Composition analysis revealed that the formed film was Cu.sub.50 Ti.sub.50.
X-ray diffraction revealed that the film was amorphous. This amorphous
CuTi thin film was exposed to the air and thereafter cleaned by Ar plasma.
An Al-0.1 at % Cu alloy was sputtered as a conductive thin film. The
sputter conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. AlCu alloy target (Cu 0.1 atm %)
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 1 Pa
Applied power: 5 W/cm.sup.2
Film thickness: 4000 .ANG.
The AlCu film thus formed was evaluated for the orientation by X-ray
diffraction. It was found that the AlCu film was a (111) orientated film
where the FWHM of a rocking curve was 0.9.degree.. Further, this thin film
was subjected to thermal treatment at 400.degree. C. for 15 minutes. As a
result, the amorphous thin film layer was crystallized and the amorphous
thin film layer disappeared. At the same time, the (111) orientation of
the AlCu film was further improved and the FWHM become 0.6.degree..
EXAMPLE 52
A TiN/Ti layer was formed on a six-inch silicon wafer as a diffusion
prevention layer. An AlTa film was formed thereon by sputtering. The
sputter conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Al/Ta binary targets
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 0.20 Pa
Applied power: 10 W/cm.sup.2
Film thickness: 100 .ANG.
Composition analysis revealed that the formed film was Al.sub.40 Ta.sub.60.
X-ray diffraction revealed that the film was amorphous. Al was sputtered
on the amorphous AlTa film as a conductive thin film under the same
conditions as those of Example 49. The Al film thus formed was evaluated
for the orientation by X-ray diffraction. It was found that the Al film
was a (111) orientated film where the FWHM of a rocking curve was
1.3.degree.. Further, this thin film was subjected to thermal treatment at
500.degree. C. for 15 minutes. As a result, the amorphous thin film layer
reacted with the conductive thin film to form Al.sub.3 Ta phase and the
amorphous thin film layer disappeared. However, the specific resistance
was not increased and orientation of the conductive thin film were
improved and the FWHM become 0.8.degree.. This exhibited that the TiN/Ti
layer suppressed reaction with silicon. The EM test was conducted under
the same conditions as those of Example 49. Even after the elapsed time of
1000 hours there was no failure.
EXAMPLE 53
A six-inch silicon wafer with a 4000 .ANG. thermal oxide film was used as a
substrate. A 100 .ANG. thick amorphous V.sub.x Al.sub.100-x, Nb.sub.x
Al.sub.100-x, Ta.sub.x Al.sub.100-x, Mo.sub.x Al.sub.100-x, or W.sub.x
Al.sub.100-x layer was formed on the substrate by means of a multi-sputter
apparatus of Example 49 while controlling electric power to be applied to
a target of Al, and V, Nb, Ta, Mo or W. Compositions of these amorphous
layers are shown in Table 17. It was confirmed by X-ray diffraction that
each layer was amorphous. As shown in Table 17, if the atomic
concentration of V, Nb, Ta, Mo or W was extremely high or low in the
amorphous layer, an inherent halo peak of amorphous state was not
observed. These samples were placed in the sputter apparatus again, and
then cleaned by Ar plasma. Thereafter a pure Al film was deposited in a
thickness of 4000 .ANG.. The (111) orientation FWHM of the deposited Al
thin film was evaluated by X-ray diffraction. The results are also shown
in Table 17. An ability of the amorphous layer to control (111)
orientation was confirmed. Subsequently, these thin films were processed
by standard PEP and RIE steps into a pattern with a 0.8 .mu.m wide wiring
as shown in FIG. 15 for the electromigration (EM) accelerated test. The EM
accelating test was conducted under conditions, a test temperature of
200.degree. C., a current density of 2.times.10.sup.6 A/cm.sup.2. When the
electric resistance of the wiring increased by 10% of the resistance just
after the test started, it was judged that this increase was a wiring
failure. As apparent from Table 17, in the Al wirings of the invention
which were formed on the amorphous underlying films, no failure was
observed even after the elapsed time of 1000 hours. This shows that the Al
wirings of the invention had the high electromigration endurance. As a
comparative example, Al was formed directly on the thermal oxide film
without deposition of an amorphous under film, and processed into the same
pattern for the EM accelating test. Under the same test conditions, in
these comparative examples, failures were observed within 10 hours.
TABLE 17
______________________________________
V.sub.x Al.sub.100-x
______________________________________
Underlying film
10 20 30 40 50 60 70
composition, X
Existence of
x .smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
x
halo peak
Al (111) FWHM
6.6.degree.
2.6.degree.
2.0.degree.
1.5.degree.
1.3.degree.
1.5.degree.
7.0.degree.
EM endurance
x .DELTA.
.DELTA.
.smallcircle.
.smallcircle.
.smallcircle.
x
______________________________________
__________________________________________________________________________
Nb.sub.x Al.sub.100-x
Underlying film
10 20 30 40 50 70 80 85 90
composition, X
Existence of
x .largecircle.
.largecircle.
.largecircle.
.largecircle.
.largecircle.
.largecircle.
.largecircle.
x
halo peak
Al(111) FWHM
6.4.degree.
2.6.degree.
1.5.degree.
1.2.degree.
1.1.degree.
1.0.degree.
1.6.degree.
2.0.degree.
6.5.degree.
EM endurance
x .DELTA.
.largecircle.
.largecircle.
.largecircle.
.largecircle.
.largecircle.
.DELTA.
x
Ta.sub.x Al.sub.100-x
Underlying film
10 20 30 50 70 80 85 90
composition, X
Existence of
x .largecircle.
.largecircle.
.largecircle.
.largecircle.
.largecircle.
.largecircle.
x
halo peak
Al(111) FWHM
6.3.degree.
2.5.degree.
1.8.degree.
1.5.degree.
1.1.degree.
1.0.degree.
1.5.degree.
6.2.degree.
EM endurance
x .DELTA.
.largecircle.
.largecircle.
.largecircle.
.largecircle.
.largecircle.
x
Mo.sub.x Al.sub.100-x
Underlying film
20 25 30 45 60 70 80 90
composition, X
Existence of
x .largecircle.
.largecircle.
.largecircle.
.largecircle.
.largecircle.
.largecircle.
x
halo peak
Al(111) FWHM
7.0.degree.
2.7.degree.
2.0.degree.
1.7.degree.
1.5.degree.
1.3.degree.
2.8.degree.
10.0.degree.
EM endurance
x .DELTA.
.DELTA.
.largecircle.
.largecircle.
.largecircle.
.DELTA.
x
W.sub.x Al.sub.100-x
Underlying film
10 15 20 30 40 50 60
composition, X
Existence of
x .largecircle.
.largecircle.
.largecircle.
.largecircle.
.largecircle.
x
halo peak
Al(111) FWHM
6.5.degree.
2.8.degree.
1.9.degree.
1.8.degree.
1.5.degree.
1.1.degree.
8.0.degree.
EM endurance
x .DELTA.
.largecircle.
.largecircle.
.largecircle.
.largecircle.
x
__________________________________________________________________________
FWHM: Full Width at Half Maximum
EM endurance:
(Test temperature, 200.degree. C.; Current density, 2 .times. 10.sup.6
A/cm.sup.2)
Endurance of 1000 hours or more; .largecircle.-
Endurance of 500 hours or more, but not more than 1000 hours; .DELTA.-
Endurance of 500 or less; x
Composition in at % unit.
EXAMPLE 54
A 1000 .ANG. thick thermal oxide film was formed on a Si (100) six-inch
substrate. Films of various alloy compositions as shown in Table 18 (a) to
(n) were formed in a thickness of 1000 .ANG. by using a mosaic target or
multi-simultaneous sputtering. Keeping vacuum, a Cu film was continuously
formed in a thickness of 4000 .ANG. and then subjected to thermal
treatment at 450.degree. C. for 30 minutes. A rocking curve of Cu (111) Cu
was measured by X-ray diffraction to examine the crystal orientation of
the Cu film thus formed. The FWHMs were shown in Table 18 (a) to (n).
For examining the crystalline properties of underlying films, samples
fabricated only with the underlying materials were evaluated by X-ray
diffraction. It was confirmed whether or not a halo peak caused by
amorphous state existed.
Conditions for the Cu film formation were shown below.
Degree of vacuum: Less than 1.times.10.sup.-7 Torr
Ar gas pressure: 1.0.times.10.sup.-3 Torr
100 MHz rf output power: 400 W
Cathode bias voltage: -300V
Film deposition rate: 40 .ANG./second
The composition of an underlying film which was formed by using a target of
the poor purity was 3N in the worst case. An element of the same group
(for example, Ta against Nb) was mainly contained as impurities, and it
was difficult that the element was isolated at the time of purification.
However, this adversely effects neither amorphous formability of the
underlying film nor the crystal orientation of Cu thereon.
For examining the reliability of the Cu wiring, a 3 .mu.m thick SiO.sub.2
film was formed on the Si substrate, and then the groove of a
four-terminal electric resistance measurement pattern was provided on the
SiO.sub.2 film as shown in FIG. 31 by PEP and RIE steps. A resistance
measurement part had groove 1.0 .mu.m wide, 4500 .ANG. deep and 1 mm long.
After the above SiO.sub.2 processing, the various under films were formed
in a thickness of 500 .ANG. by collimated sputtering. Subsequently a Cu
film was formed in a thickness of 6000 .ANG. and subjected to thermal
treatment at 450.degree. C. for 30 minutes. Excess Cu was removed by
chemical-mechanical polishing (CMP) to obtain a sample for a reliability
test.
The reliability test was conducted at a test temperature of 300.degree. C.
at a current density of 2.times.10.sup.6 A/cm.sup.2 under vacuum. The
results were also shown in Table 18. If the electrical resistance of the
wiring after the thermal treatment was converted to specific resistance
value, the value was about 1.7 .mu..OMEGA.cm. This value was substantially
the same as a bulk value of Cu. Accordingly this indicated that the
thermal treatment did not cause reaction between the underlying film and
Cu. Further, although the thermal treatment of this example was conducted
under vacuum, the thermal treatment may be conducted at a hydrogen
atmosphere or, a mixture of hydrogen and nitrogen gas (forming gas).
Moreover, although in this example a Cu film was formed continuously after
the formation of an under film, the Cu film does not need to be formed
just after the formation of the under film. That is, after the formation
of the under film, the sample may be exposed to the air and subjected to
plasma cleaning of the under film surface in vacuum for removing a natural
oxide film, followed the formation of the Cu film.
One of Ti, Zr, Hf, V, Nb, Ta or Cr elements was added to the underlying
film in the amount of 1 to 10 at % keeping the amorphous formability.
After the formation of Cu wiring, the sample was heated to 600.degree. to
750.degree. C. at a NH.sub.3 or N.sub.2 atmosphere to form a nitride film
on the Cu wiring surface and in the interface between the underlying film
and Cu film. As a result, even after a formation of a TEOS insulative
film, the electrical resistance did not increase and the oxidation of Cu
wiring was remarkably reduced.
If bias of -20 to -50V was applied to a substrate at the time of forming a
Cu film, the orientation of the Cu film was improved and a composition
range allowing excellent EM endurance was enlarged, as shown in Table
18(m) (a substrate bias was -30V).
As comparative samples, results of Cu films without an under film were
shown in Table 18(l) and (m).
TABLE 18(a)
______________________________________
Ti.sub.x Cu.sub.100-x
______________________________________
Underlying film
10 18 30 50 70 80
composition, X
Existence of
x .smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
x
halo peak
Cu film FWHM
7.2.degree.
1.6.degree.
1.4.degree.
1.1.degree.
1.0.degree.
7.8.degree.
EM endurance
x .smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
x
______________________________________
TABLE 18(b)
______________________________________
Zr.sub.x Cu.sub.100-x
______________________________________
Underlying film
10 18 30 50 70 80
composition, X
Existence of
x .smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
x
halo peak
Cu film FWHM
7.2.degree.
1.2.degree.
1.0.degree.
1.0.degree.
0.9.degree.
6.5.degree.
EM endurance
x .smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
x
______________________________________
TABLE 18(c)
______________________________________
HF.sub.x Cu.sub.100-x
______________________________________
Underlying film
10 20 40 50 70 80
composition, X
Existence of
x .smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
x
halo peak
Cu film FWHM
6.5.degree.
1.2.degree.
1.0.degree.
0.9.degree.
0.9.degree.
6.7.degree.
EM endurance
x .smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
x
______________________________________
TABLE 18(d)
______________________________________
Y.sub.x Cu.sub.100-x
______________________________________
Underlying film
5 10 12 33 50 53 60
composition, X
Existence of
x .smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
x
halo peak
Cu film FWHM
7.0.degree.
3.4.degree.
1.4.degree.
1.4.degree.
1.1.degree.
1.0.degree.
7.2.degree.
EM endurance
x .DELTA.
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
x
______________________________________
TABLE 18(e)
______________________________________
V.sub.x Co.sub.100-x
______________________________________
Underlying film
10 15 25 50 70 80 90
composition, X
Existence of
x .smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
x
halo peak
Cu film FWHM
6.8.degree.
1.9.degree.
1.3.degree.
1.5.degree.
1.2.degree.
1.7.degree.
5.8.degree.
EM endurance
x .smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
x
______________________________________
TABLE 18(f)
______________________________________
Nb.sub.x Cr.sub.100-x
______________________________________
Underlying film
20 25 35 40 45 60
composition, X
Existence of
x .smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
x
halo peak
Cu film FWHM
6.1.degree.
1.6.degree.
1.0.degree.
1.1.degree.
1.5.degree.
7.2.degree.
EM endurance
x .smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
x
______________________________________
TABLE 18(g)
______________________________________
Co.sub.x Nb.sub.100-x
______________________________________
Underlying film
30 40 45 60 70 78 85
composition, X
Existence of
x .smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
x
halo peak
Cu film FWHM
2.8.degree.
2.5.degree.
1.0.degree.
1.1.degree.
1.2.degree.
1.8.degree.
6.5.degree.
EM endurance
.DELTA.
.DELTA.
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
x
______________________________________
TABLE 18(h)
______________________________________
Ta.sub.x Cr.sub.100-x
______________________________________
Underlying film
20 25 35 40 45 60
composition, X
Existence of
x .smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
x
halo peak
Cu film FWHM
6.9.degree.
1.8.degree.
1.0.degree.
0.9.degree.
2.6.degree.
6.5.degree.
EM endurance
x .smallcircle.
.smallcircle.
.smallcircle.
.DELTA.
x
______________________________________
TABLE 18(i)
______________________________________
Ta.sub.x Co.sub.100-x
______________________________________
Underlying film
20 25 33 40 45 50 60
composition, X
Existence of
x .smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
x
halo peak
Cu film FWHM
6.degree.
1.1.degree.
0.8.degree.
1.0.degree.
1.2.degree.
2.7.degree.
7.8.degree.
EM endurance
x .smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
.DELTA.
x
______________________________________
TABLE 18(j)
______________________________________
Cr.sub.x Co.sub.100-x
______________________________________
Underlying film
45 50 60 70 80
composition, X
Existence of
x .smallcircle.
.smallcircle.
.smallcircle.
x
halo peak
Cu film FWHM
7.2.degree.
1.9.degree.
1.3.degree.
1.8.degree.
6.2.degree.
EM endurance
x .smallcircle.
.smallcircle.
.smallcircle.
x
______________________________________
TABLE 18(k)
______________________________________
Mo.sub.x Co.sub.100-x
______________________________________
Underlying film
10 20 35 45 60 80
composition, X
Existence of
x .smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
x
halo peak
Cu film FWHM
6.5.degree.
1.0.degree.
0.9.degree.
0.8.degree.
1.2.degree.
6.2.degree.
EM endurance
x .smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
x
______________________________________
TABLE 18 (l)
______________________________________
V.sub.x Co.sub.100-x
______________________________________
Underlying
15 20 35 45 60 70 90 on
film SiO.sub.2
composition, X
Existence of
x .smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
x x
halo peak
Cu film 5.0.degree.
1.0.degree.
0.9.degree.
0.8.degree.
1.0.degree.
2.5.degree.
7.0.degree.
9.0.degree.
FWHM
EM endurance
x .smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
.DELTA.
x x
______________________________________
TABLE 18 (m)
______________________________________
W.sub.x Co.sub.100-x
______________________________________
Underlying
15 20 35 45 60 70 90 on
film SiO.sub.2
composition, X
Existence of
x .smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
x x
halo peak
Cu film 2.8.degree.
0.6.degree.
0.5.degree.
0.5.degree.
0.6.degree.
1.8.degree.
6.2.degree.
7.0.degree.
FWHM
EM endurance
.DELTA.
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
x x
______________________________________
TABLE 18(n)
______________________________________
Ta.sub.x Cu.sub.100-x
______________________________________
Underlying film
10 20 40 60 80 90
composition, X
Existence of
x .smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
x
halo peak
Cu film FWHM
7.6.degree.
1.5.degree.
1.1.degree.
1.0.degree.
1.4.degree.
7.2.degree.
EM endurance
x .smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
x
______________________________________
______________________________________
Table 18(a) to 18(n)
FWHM: Full Width at Half Maximum
EM endurance:
(Test temperature, 300.degree. C.; Current density, 2 .times. 10.sup.6
A/cm.sup.2)
Endurance of 1000 hours or more;
.smallcircle. Endurance of 500 hours or more,
but not more than 1000 hours;
.DELTA. Endurance of 500 or less;
x Composition in at % unit.
______________________________________
EXAMPLE 55
Grooves with a depth of 2000 .ANG. and width of 1 .mu.m in a shape similar
to that as shown in FIG. 30(a) were formed on a six-inch silicon wafer
with a 4000 .ANG. thermal oxide film. Al was vapor deposited in a
thickness of 2000 .ANG. on this substrate. In the Al vapor deposition, a
K-cell temperature was 1200.degree. C. and a substrate temperature was
room temperature. The Al film morphology was observed by a SEM. It was
found that Al was uniformly deposited on the grooves and SiO.sub.2 surface
other than the grooves like the Al film as shown in FIG. 30(b).
Further, Al was vapor deposited in a thickness of 2000 .ANG. on a similar
substrate with grooves under the above conditions. A substrate temperature
was room temperature. Subsequently, keeping vacuum, thermal treatment at
400.degree. C. for 3 hours was conducted. It was found that the grooves of
the substrate were substantially completely filled with Al, while Al
hardly remained on SiO.sub.2 surface other than the grooves like the Al
film as shown in FIG. 30(c).
Next, Al deposited on a similar substrate with grooves in thicknesses of
2000 .ANG. and 1 ML of Bi was simultaneously deposited at the beginning of
the Al deposition. The Bi vapor deposition conditions were similar to
those of Example 31. The Al vapor deposition conditions are shown above. A
substrate temperature was room temperature. Subsequently, keeping vacuum,
thermal treatment at 200.degree. C. for 3 hours was conducted. It was
found that the grooves of the substrate were substantially completely
filled with Al, while Al hardly remained on the SiO.sub.2 surface other
than the grooves as shown in FIG. 30(d).
In the case of Ga, In, Cd, Sn, Pb or Tl, similar results were obtained.
EXAMPLE 56
Referring to FIG. 16, an embodiment will be described. Like Example 14, a
six-inch silicon wafer 1 with a 4000 .ANG. insulative film 5 formed of a
thermal oxide film was used as a substrate. An AlPt amorphous thin film 3
was formed by means of a multi-target sputter apparatus as shown in FIG.
5. The sputter conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. AlPt mosaic target
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 0.20 Pa
Applied power: 10 W/cm.sup.2
Film thickness: 100 .ANG.
Composition analysis revealed that the formed film 3 was Al.sub.40
Pt.sub.60. X-ray diffraction analysis confirmed that the film 3 was
amorphous.
Next, keeping vacuum, Pt was sputtered on the AlPt film. The sputter
conditions are as shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Pt target
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 1 Pa
Applied power: 5 W/cm.sup.2
Film thickness: 1000 .ANG.
The Pt film 33 thus formed as an under electrode was evaluated for the
orientation and crystalline properties by X-ray diffraction. The (111)
orientation FWHW was 1.3.degree. and satisfactory crystalline properties
were observed.
Further, the laminated electrode film was heat-treated at 500.degree. C.
for 15 min. in a vacuum. As a result of the treatment, the amorphous AlPt
layer 3 was disappeared by reacting with the Pt layer 33. The specific
resistance of the electrode, however, did not increase after the reaction.
The orientation thereof was improved to 1.0.degree..
Next, on the under electrode layer, a strontium titanate film 34 was formed
as a dielectric thin film by sputtering. A sintered body of strontium
titanate was used as a target. The sputter conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. SrTiO.sub.3 target
Substrate temperature: 500.degree. C.
Sputter gas: Ar/O.sub.2
Gas pressure: 1 Pa
Applied power: 5 W/cm.sup.2
Film thickness: 5000 .ANG.
The orientation and crystalline properties of the dielectric thin film were
evaluated by X-ray diffraction. The (111) orientation of Pt film 33 were
continued and the (111) orientation of FWHM was 1.2.degree.. A Pt film 35
was formed on the dielectric thin film 34 as an upper electrode by
sputtering under the above-mentioned conditions and dielectric properties
thereof were evaluated. It was found that dielectric constant and leak
current exhibited satisfactory values.
On the other hand, for comparison, the orientation FWHM of a Pt film 33
directly formed on the thermal oxide film 5 was 8.6.degree. after
heat-treatment at 500.degree. C. for 15 min. in a vacuum. When a strontium
titanate film was formed thereon under the same conditions as mentioned
above, the orientation FWHM was 9.0.degree.. The dielectric properties
thereof were evaluated. As a result, it was found that the dielectric
properties were inferior to those of example 56 of the invention. That is,
dielectric constant decreased and leak current increased.
EXAMPLE 57
We will describe this example referring to FIG. 32.
A six-inch silicon wafer 1 with a thermal oxide film 5 having a thickness
of 1000 .ANG. was used as a substrate. A TaAl film 3 was formed by means
of a multi-target sputter apparatus as shown in FIG. 5. The base pressure
was controlled to be 1.times.10.sup.-6 Pa or less. The sputtering
conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Ta/Al binary targets
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 0.20 Pa
Applied power: 10 W/cm.sup.2
Film thickness: 100 .ANG.
The TaAl film 3 thus formed was subjected to composition analysis. The
analysis revealed that the composition thereof was Ta.sub.75 Al.sub.25.
X-ray diffraction revealed that the film 3 was an amorphous thin film and
had an interatomic distance ds of 2.34 .ANG. which was determined from a
peak of halo pattern appearing in diffraction measurement.
Next, on the amorphous TaAl thin film 3, a Ti film 2a as a first layer of a
metal wiring was formed by sputtering. The sputter conditions are shown
below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Ti target
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 1 Pa
Applied power: 5 W/cm.sup.2
Film thickness: 200 .ANG.
A spacing dm of (002) plane of Ti was 2.34 .ANG.. Thus, it was found that
since .vertline.dm-ds.vertline./ds=0, the interatomic distance ds of the
amorphous thin film 3 almost matched with the spacing dm of (002) plane of
Ti film 2a.
On the Ti intermediate layer 2a, Al was sputtered as a second layer of a
metal wiring 2c. The sputter conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Al target
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 1 Pa
Applied power: 5 W/cm.sup.2
Film thickness: 4000 .ANG.
A spacing df of (111) plane of Al film 2c was 2.34 .ANG.. Thus, it was
found that since .vertline.df-ds.vertline./ds=0 the interatomic distance
ds of the amorphous film 3 matched with the spacing dt of (111) plane of
Al film 2c.
All the above lamination of films were carried out under the same vacuum
conditions. The Al film 2c thus formed was evaluated for the orientation
property by X-ray diffraction. The FWHM of a (111) rocking curve of the Al
film 2c (orientation FWHM was 0.9.degree..
On the other hand, the FWHM of a rocking curve of an Al film 2c which was
formed directly on the amorphous TaAl thin film 3 without the Ti first
layer 2a was 1.3.degree.. Thus, it was found that the first layer 2a
contributed to the improvement of orientation property. Further, when the
base pressure was not so high, high orientation Al film did not be formed,
because an oxide film was formed on the surface of the amorphous film.
Next, this multi-layered film 2a and 2c was processed into a metal wiring
for the electromigration test. Steps for preparing a test sample were as
follows: As shown in FIG. 15, a test substrate 24 having an anode 21, a
cathode 22, and a wiring part 23 connecting these electrodes was prepared
by standard lithography and RIE steps. In this case, the width of the
wiring part 23 was 0.5 .mu.m. An electric current at a current density of
2.times.10.sup.6 A/cm.sup.2 was flown to the wiring part 23 of the test
substrate 24 at a test temperature of 200.degree. C. It was confirmed that
even after the elapsed time of 2000 hours there was no failure. This
exhibits that since the Al film 2c as the metal wiring was highly oriented
the electromigration endurance was dramatically enhanced.
EXAMPLE 58
Like example 57, a six-inch silicon wafer 1 with a thermal oxide film 5
having a thickness of 1000 .ANG. was used as a substrate. A NbAl film 3
was formed by means of a multi-target sputter apparatus as shown in FIG.
5. The base pressure was controlled to be 1.times.10.sup.-6 Pa or less.
The sputter conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Nb/Al binary targets
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 0.20 Pa
Applied power: 10 W/cm.sup.2
Film thickness: 300 .ANG.
The NbAl film 3 thus formed was subjected to composition analysis. The
analysis revealed that the composition thereof was Nb.sub.50 Al.sub.50.
X-Ray diffraction revealed that the film 3 was an amorphous thin film and
had an interatomic distance ds of 2.33 .ANG. which was determined from a
peak of halo pattern appearing in diffraction measurement.
Next, on the amorphous NbAl thin film 3, a TiN film 2a as a first layer of
a metal wiring was formed by sputtering. The sputter conditions are shown
below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Ti target
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar/N.sub.2
Gas pressure: 1 Pa
Applied power: 5 W/cm.sup.2
Film thickness: 300 .ANG.
A spacing dm of (111) plane of TiN was 2.44 .ANG.. Thus, it was found that
since a .vertline.dm-ds.vertline./ds=0.047, the interatomic distance ds of
the amorphous thin film 3 approximately matched with the spacing dm of
(111) plane of TiN 2a.
On the TiN film 2a, Al was sputtered as a second layer of a metal wiring,
by the same conditions as those of example 57.
A spacing df of (111) plane of Al film 2c was 2.34 .ANG.. Thus, it was
found that since .vertline.df-ds.vertline./ds=0.004 the interatomic
distance ds of the amorphous this film 3 approximately matched with the
spacing df of (111) plane of Al film 2c.
All the above lamination of films were carried out under the same vacuum
conditions. The Al film 2c thus formed was evaluated for the orientation
property by X-ray diffraction. It was confirmed that the Al film 2c was
highly (111) oriented film having FWHM of a rocking curve of 1.0.degree..
On the other hand, the FWHM of a rocking curve of an Al film 2c which was
formed directly on the amorphous NbAl thin film 3 without the TiN first
layer 2a was 1.4.degree.. Thus, it was found that the first layer
contributed to more improvement of orientation property.
Further, this multi-layered film 2a and 2c was processed into a metal
wiring and subject to an electromigration test by using the same
conditions as those of example 57. The metal wiring also exhibited an
excellent endurance.
EXAMPLE 59
We will describe this example referring to FIG. 33.
A six-inch silicon wafer 1 with a thermal oxide film 5 having a thickness
of 1000 .ANG. was used as a substrate. A CuTi film 3 was formed by using
the same multi-target sputter apparatus as used in example 58. The base
pressure was controlled to be 1.times.10.sup.-6 Pa or less. The sputtering
conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Cu/Ti binary targets
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 0.20 Pa
Applied power: 10 W/cm.sup.2
Film thickness: 500 .ANG.
The CuTi film 3 thus formed was subjected to composition analysis. The
analysis revealed that the composition thereof was Cu.sub.58 Ti.sub.42.
X-ray diffraction revealed that the film 3 was amorphous and had an
interatomic distance ds of 2.17 .ANG. which was determined from a peak of
halo pattern appearing in diffraction measurement.
After the amorphous Cu/Ti thin film 3 was once exposed in an air, it was
cleaned by treating the surface with plasma. Then, the lamination film of
TiN/Ti was formed as a first layer of a metal wiring by sputtering. First,
a Ti film 2a was formed by sputtering Ti as a target in an Ar gas. Then, a
TiN film 2b was formed in a mixed gas of Ar/N.sub.2. The sputter
conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. Ti target
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar, Ar/N.sub.2
Gas pressure: 1 Pa
Applied power: 5 W/cm.sup.2
Film thickness: TiN/Ti=700 .ANG./200 .ANG.
First, a spacing dm1 of (002) plane of Ti film 2a was 2.34 .ANG.. Thus,
since .vertline.dm1-ds.vertline./ds=0.078, this approximately matched with
the interatomic distance ds of the amorphous CuTi thin film 3. Further,
since a spacing dm2 of (111) plane of TiN film 2b was 2.44 .ANG.,
.vertline.dm2-ds.vertline./ds=0.124, it was found that these approximately
matched with each other.
Next, an AlCu alloy as third layer of a metal wiring was sputtered. The
sputter conditions are shown below.
Sputter system: RF magnetron system
Target: 100 mm.phi. AlCu alloy target
Substrate temperature: Room temperature (25.degree. C.)
Sputter gas: Ar
Gas pressure: 1 Pa
Applied power: 5 W/cm.sup.2
Film thickness: 4000 .ANG.
The above laminations were all carried out under the same vacuum condition.
A spacing df of (111) plane of AlCu film 2c was 2.34 .ANG.. Thus,
.vertline.df-ds.vertline./ds=0.078. It was found that these approximately
matched with each other. The AlCu film 2c thus formed was evaluated for
the orientation property by X-ray diffraction. It was found that the AlCu
film 2c was highly (111) oriented film having FWHM of a rocking curve of
0.8.degree..
On the other hand, the FWHM of a rocking curve of an AlCu film 2c which was
formed directly on the amorphous CuTi thin film 3 without the first and
second layers 2a, 2b was 1.1.degree. Thus, it was found that the first and
second layers contributed to more improvement of orientation property.
Further, this laminated film was processed into a metal wiring and
subjected to an electromigration test by using the same conditions as
those of example 57. The metal wiring also exhibited an excellent
endurance.
EXAMPLES 60-70
FIG. 34 is a sectional view showing an example of an active matrix type
liquid crystal display apparatus of the invention. A method for forming
the electrode structure is shown below.
First, an amorphous thin film 203a as an underlayer was formed on a
transparent glass substrate 201 by a binary sputtering method. The
compositions thereof are shown in Table 19. The thickness of the amorphous
thin film 203a was about 100 .ANG.. However, in examples 61 and 66, the
amorphous thin film 203a as underlayer did not be formed.
On the amorphous thin film 203a, Al-0.5% Cu film was formed (in examples 61
and 66, directly on the glass substrate 201). Then, after the steps of PEP
processing, patterning processing, and wiring sintering processing, metal
wirings 202 made of a low resistant material and having a width of 6 .mu.m
and a thickness of 1500 .ANG. were formed.
Next, an amorphous thin film 203b having a thickness of 1000 .ANG. as an
upperlayer was formed on the metal wiring 202 by using the same sputtering
method as the method described above. However, in example 60, the
amorphous thin film 203b as an upperlayer did not be formed. The
compositions of the upperlayer are shown in Table 19. Then, after the
steps of PEP processing, patterning processing, and tapering processing,
an oxide film layer 204 by anodic oxidation was formed thereon. At this
time, the anodic oxidation in the examples 61 to 65 was thoroughly carried
out through the upper amorphous film 203b. And the anodic oxidation in the
examples 66 to 70 was carried out from the surface of the upper amorphous
film 203b to 900 .ANG. depth, and the remaining part which did not be
anodic-oxidized was formed as an intermediate metal layer 203b'. A
thickness of the intermediate metal layer 203b' was measured by observing
the cross-section, after all measurements were completed.
The following tests were conducted with the above samples.
Test 1. The four probe method of the resistivity measurement was conducted
for measuring the resistivity of individual samples having a shape as
shown in FIG. 35. The distance of resistivity measurement was 1 mm.
Test 2. The chemical proof test was conducted by boiling treatment of
individual samples in a cleaning liquid of H.sub.2 SO.sub.4 +H.sub.2
O.sub.2.
Test 3. In order to examine occurrence frequency of hillocks in the metal
film, the surface of individual samples thermally treated at 400.degree.
C. was observed with a microscope.
Test 4. Assuming LCD processing, a SiN passivation film 205 having a
thickness of 2000 .ANG. was formed on the oxide film layer 204, a
non-doped amorphous Si film 206 having a thickness of 3000 .ANG. was
formed on the SiN passivation film 205, n.sup.+ type amorphous Si film 207
having a thickness of 5000 .ANG. was formed on the non-doped amorphous Si
film 206, and finally a Mo film 208 having a thickness of 500 .ANG. was
formed on the n.sup.+ type amorphous Si film 207, as shown in FIG. 34. The
resulted model devices were evaluated. The test results are shown in Table
19.
As a comparison, comparatives 1 and 2 having similar structures providing
that an electrode was composed of single layer of Ta (comparative 1) or Al
(comparative 2) were prepared. The same test was conducted with these
samples. The test results are shown in Table 19.
As clearly shown in Table 19, the formation of the amorphous thin film 202a
as the underlayer contributes to improve the orientation of the electrode,
and significantly improves the hillock endurance. In addition, the
formation of the amorphous thin film 202b as the upperlayer improves the
chemical endurance of the oxide film because there is no grain boundary.
Further, the occurrence of hillocks can be prevented due to the absence of
convergence of stress.
As described above, the electrode structure of the invention exhibits low
resistivity, and has excellent chemical proof and hillock endurance.
TABLE 19
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Intermediate
Amorphous layer
Chemical
Hillock
Resist.
Composition metal layer
under
upper
proofness
endurance
(.OMEGA.)
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Example
60 Ta.sub.50 Al.sub.50
none yes none
poor good 20.8
61 Ta.sub.50 Al.sub.50
none none
yes good good 20.8
62 Ta.sub.50 Al.sub.50
none yes yes good excellent
20.7
63 Nb.sub.50 Al.sub.50
none yes yes good excellent
20.9
64 W.sub.50 Al.sub.50
none yes yes good excellent
20.9
65 Mo.sub.50 Al.sub.50
none yes yes good excellent
20.8
66 Ta.sub.50 Al.sub.50
yes none
yes good good 20.6
67 Ta.sub.50 Al.sub.50
yes yes yes good excellent
20.5
68 Nb.sub.50 Al.sub.50
yes yes yes good excellent
20.8
69 W.sub.50 Al.sub.50
yes yes yes good excellent
20.7
70 Mo.sub.50 Al.sub.50
yes yes yes good excellent
20.7
Comparative
1 Ta none none
none
good good 1280
2 Al none none
none
failure
failure
20.0
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